This is a Method of Reasoning question.
The argument is pretty abstract which is a big reason why this question is difficult. It starts with other people’s position (OPP). Some researchers claim that people tend to gesture more when they speak about what would typically be considered physical concepts than abstract ones. Okay, so according to these researchers, someone speaking about cats and dogs will tend to gesture more than when speaking about prime numbers. That sounds plausible, I guess.
Now the author transitions to her argument. She opens with her conclusion that to point out that such a correlation (that’s OPP, the correlation between gesture and physical concepts) is far from universal is insufficient to reject OPP. In other words, pointing out exceptions to the correlation isn’t enough to reject the correlation. That also sounds right. In general, a correlation isn’t ironclad. There will be nonconforming exceptions. That’s my reasoning, not the author’s. Before we get to the author’s premise, note that the author is actually defending OPP! Is it Christmas in July? What is happening? The author’s conclusion is basically “Here’s one ineffective line of attack on OPP. You can’t just point out that the correlation isn’t universal and think that constitutes a successful attack on the correlation.”
Okay, now that we’ve gotten over the shock, what is her premise? How does she support that conclusion? “Because” some people perceive words like “comprehension” as a physical action like grasping something, whereas others perceive it as an abstract action like a state of understanding. Alright, that works. She’s saying you can’t attack OPP by pointing out apparent counterexamples because it’s not clear that they even are counterexamples. Take “comprehension,” for instance. Someone gestures a lot when talking about comprehension, whereas someone else gestures a little. Is that a counterexample to the correlation that gesture goes with physical concepts? Well, not necessarily because it could be that the person gesturing a lot perceives “comprehension” as a physical act, whereas a person not gesturing much perceives “comprehension” as an abstract act. In that case, this would fit with the correlation.
Let’s look at the answers now.
Answer Choice (A) can be analyzed piecemeal by looking at the conclusion and premise descriptors separately. (A) says the argument “appeals to X in an attempt to show Y.” We appeal to premises to show conclusions, not the other way around. So the first part is the premise descriptor and the second part the conclusion descriptor. Is there an appeal to the ambiguity of a word in the premise? Yes. “Comprehension” is the word. And it’s ambiguous whether that’s perceived as a physical or abstract concept. Great, let’s now look at the conclusion descriptor. “In an attempt to show that a correlation is universal.” But that’s wrong. The author’s conclusion isn’t trying to show that the correlation is universal. She’s just fending off one particular attack on it being universal. There’s a difference between affirmatively proving a position, which she’s not doing here, and pointing out that a class of arguments is weak, which she is doing here.
Answer Choice (B) can also be analyzed piecemeal. The premise descriptor says that the argument “appeals to a universal psychological generalization.” But that’s not an accurate description of the premise. If anything, the premise is a rejection of a universal psychological generalization. The premise declares that some people perceive a word one way and others another. The only part of the stimulus that might be accurately characterized as a universal psychological generalization is OPP. That’s enough to eliminate (B). The conclusion descriptor says, “in an attempt to support a claim about the use of gestures.” That’s also an inaccurate description. The conclusion is that one claim isn’t powerful enough to reject another claim.
Correct Answer Choice (C) can also be analyzed piecemeal. (C) says the argument “cites X to try to show Y.” We cite premises to reach conclusions, so the first part is the premise descriptor and the second part the conclusion descriptor. The premise descriptor says, “citing a psychological fact.” Yes, that’s true. The psychological fact cited is that people perceive words like “comprehension” differently. The conclusion descriptor says, “to try to reconcile a generalization with apparently disconfirming evidence.” That’s also true. That’s not the most direct description of the conclusion but that’s certainly the underlying reasoning. The reason why the author says this particular line of attack on OPP fails is because what looks like disconfirming evidence (the variable rates of gestures with the word “comprehension”) may be reconciled with the generalization (the correlation) by realizing that people perceive the word differently.
Answer Choice (D) can also be analyzed piecemeal. (D) says the argument “advocates X by attempting to demonstrate that Y.” We advocate conclusions so the first part is the conclusion descriptor and the second part the premise descriptor. But the conclusion descriptor is inaccurate. The author’s conclusion isn’t an explanation of a phenomenon. Her premise, on the other hand, can be viewed as an explanation of a phenomenon. Her premise explains why there’s inconsistency between gesturing and articulations of certain words like “comprehension.” The explanation is that people perceive those kinds of words differently. Yet (D) describes that premise inaccurately as “attempting to demonstrate that other possible explanations are implausible.”
Answer Choice (E) says the argument offers a reason for believing that a widely accepted generalization requires still more supporting evidence. First of all, what’s “widely accepted generalization”? The correlation claimed by “some researchers”? There’s no evidence that that’s widely accepted. Already inaccurate. Second, the author isn’t arguing for the claim that the correlation requires more supporting evidence. Rather, as already discussed, the author is just protecting that correlation from one particular mode of attack.
This is an SA question.
The argument opens with OPA. “Many people” believe that independent films have more integrity as work than major studio productions because indies are less conventional. Okay, great. That’s OPA.
The author (filmmaker) transitions to her argument with “however.” The premise is that indie filmmakers’ need to make a profit affects their artistic decisions. The conclusion is that indie films do not have absolute artistic integrity.
This looks a lot like a PSA question. The premise can be represented as P and the conclusion as C. We need to build a P→C bridge. If profit affects artistic decisions, then there is no absolute artistic integrity. Or something like that.
Correct Answer Choice (B) says if any of the artistic decisions made in creating something were affected by the need to make profits, then that creation does not have absolute integrity as a work of art. That works as a P→C bridge. As is often the case, the correct answer covers more than what we need. (B) covers any artistic decision, not just the ones involved in filmmaking. But that’s fine.
Answer Choice (A) can be eliminated on its logic alone. You can either notice that the sufficient condition here is “artistic decision unaffected by profit needs” or notice that the necessary condition here is “creation has absolute artistic integrity.” Both are wrong. The sufficient condition is supposed to be P, not /P. The necessary condition is supposed to be C, not /C. This is a recurring type of wrong answer for SA and PSA questions. It’s sufficiency-necessity confusion.
Answer Choice (C) can be eliminated by noticing that it’s a comparative statement. We need a logically tight bridge. (C) says that individual creations tend to have more artistic integrity than group creations. Okay, but the argument isn’t concerned with comparing “individual creations” to “group creations.” Only OPA talks about indie films in comparison to major studio productions. No doubt major studio productions are “group creations.” But don’t assume that indie films are “individual creations.” They probably involve fewer people but they probably still involve more than one person.
Answer Choice (D) precludes something as having an effect on artistic integrity. (D) precludes the “unconventionality” of a creation as having an effect on artistic integrity. Okay, now what? The argument is assuming that profit requirements have an effect on artistic integrity. More specifically, it assumes that the effect is that it taints artistic integrity.
Answer Choice (E) is a conditional constructed with “unless.” Translated to an “if...then...” construction, we get, “If artistic decisions were affected by views about what is conventional, then no artistic integrity.” The problem here is that the premises in the argument do not trigger the sufficient condition. All we know about indie filmmakers is that they need to make a profit, which affects their artistic decisions. It’s a further assumption that the need to make a profit amounts to a “view about what is conventional.” The necessary condition in (E) is more than what’s needed, but that’s not a problem for SA answers. If we could have triggered the sufficient condition here, then we could have drawn the conclusion that a creation has no artistic integrity. That would have necessarily implied that it doesn’t have absolute artistic integrity.
Because independent filmmakers need to make profits, which influences the artistic decisions made in creating most independent films.
To go further, we can anticipate a more specific connection between the premise and conclusion. The premise tells us that most independent films involve artistic decisions that are influenced by the need for profits. To make the argument valid, we want to show that this quality — having artistic decisions influenced by the need for profits — implies a lack of absolute integrity as an artwork.
A
A creation has absolute integrity as a work of art if the artistic decisions made in creating it were unaffected by the need to make profits.
B
If any of the artistic decisions made in creating something were affected by the need to make profits, then that creation does not have absolute integrity as a work of art.
C
The creations of individuals have more integrity as works of art, on average, than those of groups.
D
The unconventionality of a creation has no bearing on its integrity as a work of art.
E
A creation has no integrity as a work of art unless the artistic decisions made in creating it were unaffected by views about what is conventional.
This is an SA question.
The argument opens with OPA. “Many people” believe that independent films have more integrity as work than major studio productions because indies are less conventional. Okay, great. That’s OPA.
The author (filmmaker) transitions to her argument with “however.” The premise is that indie filmmakers’ need to make a profit affects their artistic decisions. The conclusion is that indie films do not have absolute artistic integrity.
This looks a lot like a PSA question. The premise can be represented as P and the conclusion as C. We need to build a P→C bridge. If profit affects artistic decisions, then there is no absolute artistic integrity. Or something like that.
Correct Answer Choice (B) says if any of the artistic decisions made in creating something were affected by the need to make profits, then that creation does not have absolute integrity as a work of art. That works as a P→C bridge. As is often the case, the correct answer covers more than what we need. (B) covers any artistic decision, not just the ones involved in filmmaking. But that’s fine.
Answer Choice (A) can be eliminated on its logic alone. You can either notice that the sufficient condition here is “artistic decision unaffected by profit needs” or notice that the necessary condition here is “creation has absolute artistic integrity.” Both are wrong. The sufficient condition is supposed to be P, not /P. The necessary condition is supposed to be C, not /C. This is a recurring type of wrong answer for SA and PSA questions. It’s sufficiency-necessity confusion.
Answer Choice (C) can be eliminated by noticing that it’s a comparative statement. We need a logically tight bridge. (C) says that individual creations tend to have more artistic integrity than group creations. Okay, but the argument isn’t concerned with comparing “individual creations” to “group creations.” Only OPA talks about indie films in comparison to major studio productions. No doubt major studio productions are “group creations.” But don’t assume that indie films are “individual creations.” They probably involve fewer people but they probably still involve more than one person.
Answer Choice (D) precludes something as having an effect on artistic integrity. (D) precludes the “unconventionality” of a creation as having an effect on artistic integrity. Okay, now what? The argument is assuming that profit requirements have an effect on artistic integrity. More specifically, it assumes that the effect is that it taints artistic integrity.
Answer Choice (E) is a conditional constructed with “unless.” Translated to an “if...then...” construction, we get, “If artistic decisions were affected by views about what is conventional, then no artistic integrity.” The problem here is that the premises in the argument do not trigger the sufficient condition. All we know about indie filmmakers is that they need to make a profit, which affects their artistic decisions. It’s a further assumption that the need to make a profit amounts to a “view about what is conventional.” The necessary condition in (E) is more than what’s needed, but that’s not a problem for SA answers. If we could have triggered the sufficient condition here, then we could have drawn the conclusion that a creation has no artistic integrity. That would have necessarily implied that it doesn’t have absolute artistic integrity.
This is an NA question.
The stimulus proceeds in order from premises to the conclusion. Bovine remains were found in a certain place back when that place had an arid (dry) climate. There were people present at that time in that region but no other large mammals. If there were natural sources of water available, there would also have been other large mammals. But we already know there were no other large mammals. We can contrapose to infer that there were no natural sources of water available.
The argument hence concludes that these bovines had been domesticated (people were providing it water) and the people there were no longer exclusively hunter-gatherers.
This sounds like a decent argument, right? If you think so, then you’re already supplying the missing assumption, that if they weren’t domesticated, they couldn’t have survived. But really, we don’t know that. Perhaps they were wild and crafty and survived by taking advantage of man-made water sources. That would be bad for the argument. So we do need to supply the assumption connecting the premises (arid climate, no natural water sources) to the conclusion (domestication).
This is what Correct Answer Choice (A) does. Translating the “unless,” (A) says that if the bovines weren’t domesticated, they were unlikely to exist in a region without natural sources of water. The premises fail the necessary condition (the bovines likely did exist), which allows us to infer the failure of the sufficient condition (the bovines were domesticated) as the conclusion. This connects the premises to the conclusion. More than that, it truly is necessary. If we deny this conditional relationship, we’re asserting that it’s possible for the bovines to be wild yet survive anyway in this arid region. That’s exactly the possibility that we contemplated above that would ruin the argument.
Answer Choice (B) says that domesticating animals is one of the first things that a society must do when transitioning from hunter-gatherer to agriculture. This is unnecessary. Why first? Why not second or third? Also notice that it’s trying to bridge the two concepts in the conclusion, that of “domestication” and that of “no longer exclusively hunter-gatherer.” But we don’t need to build that bridge. They are already connected by their definitions. Domestication necessarily implies no longer exclusively hunter-gatherer. A culture that practices domestication cannot be exclusively hunter-gatherer.
Answer Choice (C) says that other large mammals would have been able to inhabit this arid region with the help of humans. So, like what? Horses? That’s required? No, it’s not. Let’s imagine this were false. Even with the help of humans, this arid region could not have supported horses. Who cares? The argument is still as strong as it ever was.
Answer Choice (D) says no human culture can be a hybrid of agriculture and hunter-gatherer. So (D) is claiming that all human cultures must be exclusively either an agricultural society or else a hunter-gatherer society. You can’t do both. But that’s silly. It doesn’t affect the argument if there was a culture that both planted wheat and hunted meat. In fact, the conclusion in the stimulus claims that these people are a kind of hybrid culture.
Answer Choice (E) says that a domesticated cow doesn’t need as much water as a wild cow. This might strengthen the argument? Like their modest demand for water might help explain why humans were able to domesticate them in an arid climate. But it’s not necessary. Imagine this were false and the cows required the same amount of water, regardless of whether they were domesticated or wild. The argument would still be fine. It would just have been not as easy to domesticate them.
This is an NA question.
The stimulus proceeds in order from premises to the conclusion. Bovine remains were found in a certain place back when that place had an arid (dry) climate. There were people present at that time in that region but no other large mammals. If there were natural sources of water available, there would also have been other large mammals. But we already know there were no other large mammals. We can contrapose to infer that there were no natural sources of water available.
The argument hence concludes that these bovines had been domesticated (people were providing it water) and the people there were no longer exclusively hunter-gatherers.
This sounds like a decent argument, right? If you think so, then you’re already supplying the missing assumption, that if they weren’t domesticated, they couldn’t have survived. But really, we don’t know that. Perhaps they were wild and crafty and survived by taking advantage of man-made water sources. That would be bad for the argument. So we do need to supply the assumption connecting the premises (arid climate, no natural water sources) to the conclusion (domestication).
This is what Correct Answer Choice (A) does. Translating the “unless,” (A) says that if the bovines weren’t domesticated, they were unlikely to exist in a region without natural sources of water. The premises fail the necessary condition (the bovines likely did exist), which allows us to infer the failure of the sufficient condition (the bovines were domesticated) as the conclusion. This connects the premises to the conclusion. More than that, it truly is necessary. If we deny this conditional relationship, we’re asserting that it’s possible for the bovines to be wild yet survive anyway in this arid region. That’s exactly the possibility that we contemplated above that would ruin the argument.
Answer Choice (B) says that domesticating animals is one of the first things that a society must do when transitioning from hunter-gatherer to agriculture. This is unnecessary. Why first? Why not second or third? Also notice that it’s trying to bridge the two concepts in the conclusion, that of “domestication” and that of “no longer exclusively hunter-gatherer.” But we don’t need to build that bridge. They are already connected by their definitions. Domestication necessarily implies no longer exclusively hunter-gatherer. A culture that practices domestication cannot be exclusively hunter-gatherer.
Answer Choice (C) says that other large mammals would have been able to inhabit this arid region with the help of humans. So, like what? Horses? That’s required? No, it’s not. Let’s imagine this were false. Even with the help of humans, this arid region could not have supported horses. Who cares? The argument is still as strong as it ever was.
Answer Choice (D) says no human culture can be a hybrid of agriculture and hunter-gatherer. So (D) is claiming that all human cultures must be exclusively either an agricultural society or else a hunter-gatherer society. You can’t do both. But that’s silly. It doesn’t affect the argument if there was a culture that both planted wheat and hunted meat. In fact, the conclusion in the stimulus claims that these people are a kind of hybrid culture.
Answer Choice (E) says that a domesticated cow doesn’t need as much water as a wild cow. This might strengthen the argument? Like their modest demand for water might help explain why humans were able to domesticate them in an arid climate. But it’s not necessary. Imagine this were false and the cows required the same amount of water, regardless of whether they were domesticated or wild. The argument would still be fine. It would just have been not as easy to domesticate them.
This is an NA question.
The argument begins with a pretty long sentence that turns out to be just context. It tells us similarities between the “chorus” in a play and the “narrator” in a novel. They share many similarities. Both introduce a point of view untied to other characters. Both allow the author to comment on the characters’ actions and to introduce other information.
With the word “however,” we transition from context to argument. And it’s a simple argument with one premise and one conclusion. The premise is that the chorus sometimes introduces information inconsistent with the rest of the play. The conclusion is that the chorus is not equivalent to the narrator.
What’s the missing link? It’s a premise-to-conclusion bridge. We have to assume that the narrator never introduces inconsistent information.
This is what Correct Answer Choice (D) provides. It says that information introduced by a narrator can never be inconsistent with the rest of the information in the novel. That’s it. And with this assumption, the argument is valid. This is an example of where a necessary assumption is also a sufficient assumption. This tends to happen when the argument structure is simple and therefore there is only one assumption to bridge the premise to the conclusion.
Answer Choice (A) is attractive. It says the narrator is never deceptive. This sounds necessary, right? Because the premise said the chorus was deceptive and so in order for the narrator to not be equivalent with the chorus, it must be that the narrator is never deceptive. But no, this isn’t necessary. The premise just said that the chorus sometimes introduces information that’s inconsistent with the rest of the play. That doesn’t mean the chorus is being deceptive. We’re projecting intent onto the chorus without evidence. Maybe they’re trying to deceive. Maybe they’re trying to help us see through the deception of a character in the play. The chorus is telling the truth to the character’s lies. So no, (A) is not necessary. The narrator can be deceptive and the conclusion can still follow that the narrator is not equivalent to the chorus.
This also explains why Answer Choice (E) is unnecessary. (E) claims that authors sometimes use choruses to mislead audiences.
Answer Choice (B) says the voice of a narrator is sometimes necessary in plays that employ a chorus. What? Get out of here with this basic BS. This is just a mish-mash of ideas from the stimulus. There’s no reason why a play that employs a chorus must also employ a narrator.
Answer Choice (C) claims that information necessary for the audience to understand the events in a play is sometimes introduced by the chorus. No, this isn’t necessary. Let’s say that all the information introduced by the chorus is “extra” information: nice to have but not required for the audience to understand the play. What impact would that have on the argument? Not much. The narrator can still be not equivalent to the chorus as long as the narrator does what (D) says.
This is an NA question.
The argument begins with a pretty long sentence that turns out to be just context. It tells us similarities between the “chorus” in a play and the “narrator” in a novel. They share many similarities. Both introduce a point of view untied to other characters. Both allow the author to comment on the characters’ actions and to introduce other information.
With the word “however,” we transition from context to argument. And it’s a simple argument with one premise and one conclusion. The premise is that the chorus sometimes introduces information inconsistent with the rest of the play. The conclusion is that the chorus is not equivalent to the narrator.
What’s the missing link? It’s a premise-to-conclusion bridge. We have to assume that the narrator never introduces inconsistent information.
This is what Correct Answer Choice (D) provides. It says that information introduced by a narrator can never be inconsistent with the rest of the information in the novel. That’s it. And with this assumption, the argument is valid. This is an example of where a necessary assumption is also a sufficient assumption. This tends to happen when the argument structure is simple and therefore there is only one assumption to bridge the premise to the conclusion.
Answer Choice (A) is attractive. It says the narrator is never deceptive. This sounds necessary, right? Because the premise said the chorus was deceptive and so in order for the narrator to not be equivalent with the chorus, it must be that the narrator is never deceptive. But no, this isn’t necessary. The premise just said that the chorus sometimes introduces information that’s inconsistent with the rest of the play. That doesn’t mean the chorus is being deceptive. We’re projecting intent onto the chorus without evidence. Maybe they’re trying to deceive. Maybe they’re trying to help us see through the deception of a character in the play. The chorus is telling the truth to the character’s lies. So no, (A) is not necessary. The narrator can be deceptive and the conclusion can still follow that the narrator is not equivalent to the chorus.
This also explains why Answer Choice (E) is unnecessary. (E) claims that authors sometimes use choruses to mislead audiences.
Answer Choice (B) says the voice of a narrator is sometimes necessary in plays that employ a chorus. What? Get out of here with this basic BS. This is just a mish-mash of ideas from the stimulus. There’s no reason why a play that employs a chorus must also employ a narrator.
Answer Choice (C) claims that information necessary for the audience to understand the events in a play is sometimes introduced by the chorus. No, this isn’t necessary. Let’s say that all the information introduced by the chorus is “extra” information: nice to have but not required for the audience to understand the play. What impact would that have on the argument? Not much. The narrator can still be not equivalent to the chorus as long as the narrator does what (D) says.
This is an NA question.
The stimulus opens with context that the premises call upon with a referential phrase. To establish a human colony on Mars, it requires the presence of a tremendous quantity of basic materials on Mars. And then we need to assemble those materials. The premise states that the costs of transporting those materials through space would be very high. Therefore, the argument concludes that it wouldn’t be economically feasible to establish a colony on Mars.
The assumption is that the costs in the premises are a consideration that matters. What are those costs again? Costs of “transporting material through space.” Now, why would we need to transport materials through space? Because a Martian colony requires a tremendous amount of basic materials. But again, why must we transport that “tremendous amount of basic materials” through space? The assumption is that those materials cannot be found on Mars.
This is absolutely necessary for the premises to even matter to the conclusion. This is what Correct Answer Choice (E) says. That Mars isn’t a practical source of the basic materials required for establishing human habitation there. If Mars were, then there’d be no need to transport those materials through space.
(E) seems pretty obvious once you get there. But the hard part is in getting past the other trap answers.
Answer Choice (A) is one such trap. It uses “only if” to lay out a necessary condition for establishing human habitation on Mars: the decrease in cost of transporting materials from Earth to Mars. This sounds good but it isn’t necessary. First, note that the conclusion didn’t claim that it would be physically impossible to colonize Mars. Rather, just that it would be economically infeasible. Economically infeasible means highly unlikely, but it doesn’t mean impossible. Economic constraints are softer than physical or technological constraints. Economic constraints are a matter of collective resource allocation. Physical or technological constraints are imposed by what knowledge we have access to. Second, note that the premises cited the costs of transportation through space. Surely Earth to Mars is through space but so is the moon to Mars. And so is the asteroid belt to Mars. If the materials aren’t even coming from Earth in the first place, then why should we care about the transportation costs of Earth to Mars?
Answer Choice (B) is another trap. It says that the cost of transportation through space (note already the improvement upon (A)) isn’t expected to decrease in the near future. Again, this sounds good. Don’t we need the costs to not decrease? Well, first notice that (B) isn’t about what will actually happen to the costs. It’s about what we expect to happen to the costs. We don’t need expectations to point in any particular direction. We need actual costs to not decrease. Second, even if actual costs decrease in the near future, the argument can still survive as long as the costs don’t decrease too much. For example, imagine if the costs decrease by 0.01%. That’s presumably not enough of a decrease to make a difference. In order to hurt the argument, we need to have the costs decrease to the point of being economically feasible to transport enough basic materials to Mars.
Answer Choice (C) claims that Earth is the only source of basic materials necessary for a Martian colony. This is a classic Strengthen answer in an NA question. If (C) were true, then that definitely helps the argument. Earth is the only source of raw materials and therefore, to get those materials to Mars, we must transport them through space. But this isn’t necessary. What if one of Mars' two moons had the requisite materials? That would still require transportation through space and so the argument would still survive. (C) isn’t necessary.
Answer Choice (D) says that no significant benefit would result from establishing a human colony on Mars. This isn’t necessary. The argument didn’t express a value judgment. It wasn’t about the pros and cons of establishing a Mars colony or whether we should do it. It was just an argument about the costs and economic feasibility of such an endeavor. (D) is not only unnecessary, it is also irrelevant.
This is an NA question.
The stimulus opens with context that the premises call upon with a referential phrase. To establish a human colony on Mars, it requires the presence of a tremendous quantity of basic materials on Mars. And then we need to assemble those materials. The premise states that the costs of transporting those materials through space would be very high. Therefore, the argument concludes that it wouldn’t be economically feasible to establish a colony on Mars.
The assumption is that the costs in the premises are a consideration that matters. What are those costs again? Costs of “transporting material through space.” Now, why would we need to transport materials through space? Because a Martian colony requires a tremendous amount of basic materials. But again, why must we transport that “tremendous amount of basic materials” through space? The assumption is that those materials cannot be found on Mars.
This is absolutely necessary for the premises to even matter to the conclusion. This is what Correct Answer Choice (E) says. That Mars isn’t a practical source of the basic materials required for establishing human habitation there. If Mars were, then there’d be no need to transport those materials through space.
(E) seems pretty obvious once you get there. But the hard part is in getting past the other trap answers.
Answer Choice (A) is one such trap. It uses “only if” to lay out a necessary condition for establishing human habitation on Mars: the decrease in cost of transporting materials from Earth to Mars. This sounds good but it isn’t necessary. First, note that the conclusion didn’t claim that it would be physically impossible to colonize Mars. Rather, just that it would be economically infeasible. Economically infeasible means highly unlikely, but it doesn’t mean impossible. Economic constraints are softer than physical or technological constraints. Economic constraints are a matter of collective resource allocation. Physical or technological constraints are imposed by what knowledge we have access to. Second, note that the premises cited the costs of transportation through space. Surely Earth to Mars is through space but so is the moon to Mars. And so is the asteroid belt to Mars. If the materials aren’t even coming from Earth in the first place, then why should we care about the transportation costs of Earth to Mars?
Answer Choice (B) is another trap. It says that the cost of transportation through space (note already the improvement upon (A)) isn’t expected to decrease in the near future. Again, this sounds good. Don’t we need the costs to not decrease? Well, first notice that (B) isn’t about what will actually happen to the costs. It’s about what we expect to happen to the costs. We don’t need expectations to point in any particular direction. We need actual costs to not decrease. Second, even if actual costs decrease in the near future, the argument can still survive as long as the costs don’t decrease too much. For example, imagine if the costs decrease by 0.01%. That’s presumably not enough of a decrease to make a difference. In order to hurt the argument, we need to have the costs decrease to the point of being economically feasible to transport enough basic materials to Mars.
Answer Choice (C) claims that Earth is the only source of basic materials necessary for a Martian colony. This is a classic Strengthen answer in an NA question. If (C) were true, then that definitely helps the argument. Earth is the only source of raw materials and therefore, to get those materials to Mars, we must transport them through space. But this isn’t necessary. What if one of Mars' two moons had the requisite materials? That would still require transportation through space and so the argument would still survive. (C) isn’t necessary.
Answer Choice (D) says that no significant benefit would result from establishing a human colony on Mars. This isn’t necessary. The argument didn’t express a value judgment. It wasn’t about the pros and cons of establishing a Mars colony or whether we should do it. It was just an argument about the costs and economic feasibility of such an endeavor. (D) is not only unnecessary, it is also irrelevant.
This is an NA question.
This is a very difficult argument to understand substantively. Let’s first approach this question by breaking it up into its parts. Conveniently, it progresses in order from minor premise to major premise to main conclusion. The two conclusion indicator words “thus” and “therefore” help us recognize this.
There may be a way to get to the right answer without fully understanding the argument substantively, but I wouldn’t bank on it. You’ll have to pick up in the main conclusion the new reference to “other characteristics.” What other characteristics? We’ve only talked about a star’s brightness. So the “other characteristics,” whatever they may be, had better be determinable.
If you picked up on that, then you’re probably down to Answer Choice (B) and Correct Answer Choice (D). The problem with (B) is that it’s too specific and hence unnecessary. We don’t need “differences in the elements each is burning” to be detectable from Earth. We just need some difference to be detectable from Earth, like how (D) has it.
Okay, but let’s back up and try to actually understand this argument.
The minor premise tells us that the distance between Earth and a distant galaxy overwhelms the distance between Earth and any object in that distant galaxy. Imagine you’re on a tiny island and we’re trying to measure the distance between you and two people on a different faraway tiny island. They’re not equidistant from you. One of them is actually closer, because, say, one is standing at the shore and the other is standing on the other side of the island. But the first sentence is saying that the distance between the two islands is so vast that that’s the only thing that really matters. The islands themselves are so small and the vast space between the islands so large that it hardly matters where anyone is standing on their islands. That difference is so small that it’s negligible.
So it follows that if two stars are in the same distant galaxy (two people on the same distant island), then the distance between those two stars to Earth will in effect be the same (because whatever difference is negligible). But if we still observe a difference in their brightness, that difference can’t be due to their (negligibly different) distance. It must be due to their actual brightness as in how bright they’re actually burning and not just how bright they appear to be.
Now the argument reaches for its main conclusion. It concludes that we should be able to figure out the correlation between two stars' relative actual brightness and the two stars’ other characteristics. We see “other characteristics” appear out of nowhere. We did talk about brightness and how if two stars are in the same distant galaxy, we can in effect treat them as being equidistant from Earth in terms of their brightness. But in order to correlate their brightness with “other characteristics,” we first have to be able to detect and measure those “other characteristics.”
Again, this is what Correct Answer Choice (D) picks up on. It says that there are stars in distant galaxies that have characteristics, other than brightness, discernible from Earth. This must be true. If this were false, that would mean that we could discern only a distant star’s brightness and nothing else. If that’s true, then we would be unable to correlate brightness with anything else.
Note that (D) doesn’t care to specify what the “characteristics” are. That’s good because the conclusion didn’t care to specify either. This is what makes Answer Choice (B) unnecessary. While (B) would certainly strengthen the argument, we don’t need the differences in the elements each is burning to be detectable from Earth. Who knows what “other characteristics” the conclusion wanted to correlate with brightness? Maybe it’s the elements that each is burning. Maybe it’s the color of the stars, their size or mass, or their temperature. It could be any of those characteristics that need to be detectable from Earth.
Answer Choice (A) says that if two stars are in two different galaxies... Eh, we can stop. We don’t care. The argument cares about two stars in the same distant galaxy. (A) talks about two stars in two different (near or far?) galaxies. Whatever else (A) is about to say for these two stars will be irrelevant so you should move on to the next answer.
But for review, we can negate this and see that it has no impact on the argument. So what if it is possible to determine their distances from Earth? That doesn’t hurt the argument.
Answer Choice (C) is similarly irrelevant for it talks about stars in our own galaxy. Again, for the same reasons as in (A), we don’t care. We should move on.
If we negate (C), that’s just fine for the argument. It would be absolutely bizarre if all the stars in the Milky Way were all approximately the same distance from Earth but it wouldn’t affect the argument.
Answer Choice (E) can also be similarly eliminated as soon as you see that it’s talking about stars that are significantly different in distance from Earth. The argument contemplated two stars that are not significantly different in distance from Earth. That’s what the sub-argument established by placing the two stars in distant galaxies to begin with. We should move on.
(E) goes on to say that if there are significant differences in how far away two stars are from Earth, then those stars will differ significantly in apparent brightness. This isn’t required. It’s fine for the argument if two stars of significant difference in distance from Earth are about the same in brightness. The argument contemplated two stars of insignificant difference in distance but significant difference in brightness. After all, a major assumption of the argument is that distance is only one factor in determining a star’s brightness.