This question stem is a little unusual. If you struggled to identify this as a Necessary Assumption question, think about the conditional function of the “unless.” The answer choice is the condition following the “unless,” so we could negate sufficient to say something like, “If which one of the follow answers is not assumed, then the conclusion cited does not follow.” If we contrapose this, we get, “If the conclusion cited follows, then which answer must be assumed?” This puts the answer choice in the necessary condition of the conditional. So, we know this is a necessary assumption question.
We see that there are a number of inconsistencies in a history book. From this, these scholars conclude that the author must have been drawing from multiple sources.
And that’s it. That’s the whole stimulus. This is a very simple argument: Inconsistencies, therefore multiple sources. Structurally, this is just “A therefore B.” These are very common LSAT arguments, and they have never done the work of tying the relevancy of the premise to the conclusion. And they always fail as arguments for this reason. Does the premise have anything to do with the conclusion? These arguments do not establish that connection. One assumption always necessary for these is “If A then B.” It isn’t a very interesting assumption, but it is necessary. Here, that is “If inconsistencies then multiple sources used.” Notice this is also sufficient. That can cause some alarm, but do not fear. With this particular argument structure, such an assumption will be both sufficient and necessary. They don’t have to give us this exactly, so we will still keep an open mind in the answers, but these arguments are so simplistic, they do not create much opportunity for alternatives.
Answer Choice (A) We don’t care about what authors “generally” do. Maybe they generally ignore discrepancies. Or maybe they generally convey the discrepancies and discuss the reason for the discrepancies with commentary on the likely reliability of their different sources. Who cares what they generally do or why? Not us. We care about what this one particular author actually did on this one particular occasion. Any given generality is welcome to be true, but need not be. If it doesn’t have to be true, it isn’t necessary.
Answer Choice (B) Again, this is just not something we care about. The average reader is welcome to spot these inconsistencies. They are equally welcome to overlook them. We care about the number of sources the author used, and the reader simply has nothing to do with that.
Correct Answer Choice (C) A and B tried to tell us something that does happen. This is telling us something that did not: The author did not use a single source which itself contained the inconsistencies in our author’s book. This has to be true. This is the right answer. If our author did use one source which itself contained the same inconsistencies as the book in question, then these inconsistencies need not result from inconsistencies among multiple sources. It seems quite reasonable that the inconsistencies could have resulted from the same inconsistencies from this one source.
Answer Choice (D) This is wrong for similar reasons as A and B. We do not care one way or the other if our author was aware that inconsistencies could arise. With our without their awareness, the inconsistencies arose. That’s all that really matters here. Their awareness has no bearing on the source of the inconsistencies.
Answer Choice (E) This is wrong for the exact same reason as everything else. In D, the author’s awareness of the possibility of inconsistencies doesn’t matter. Here, the author’s awareness of all the possible source materials doesn’t matter. If there was one book relevant to the subject that they didn’t know about, does that mean anything for our argument relating to the source of the inconsistencies? It does not.
This is a most strongly supported question, since the stem asks: The statements above, if true, most strongly support which one of the following hypotheses?
The stimulus gives us some information about insectivorous plants. These are plants which can trap and digest insects (think Venus flytraps), and we’re told that they can survive in soils that are too poor in minerals for non-insectivorous plants. Interesting! This phenomenon is made even stranger when the next sentence lets us know that insectivorous plants have practically the same mineral requirements! We should infer from this that either the minerals must be coming from somewhere else, or the insectivorous plants are more efficient at getting minerals from poor soil. Our job is to select the answer choice whose hypothesis explains this phenomenon with the least assumptions required. Let’s see what we get!
Answer Choice (A) This doesn’t help our mineral problem, since we still don’t know how having lots of insects around would give the plant its required minerals.
Answer Choice (B) We’ve been told they can survive in these poor soils, but nothing about whether they do particularly well in them. Regardless, this does nothing to explain how they can survive while having the same mineral needs as the plants that can’t survive.
Answer Choice (C) But we’ve been told that the minerals required by the two types of plants are basically the same!
Answer Choice (D) This does nothing to explain our phenomenon, while also making a ton of assumptions. Maybe the areas with poor soil are rarer!
Correct Answer Choice (E) If they can get their minerals from the insects they digest, that would explain the difference in survival ability between them and the plants that don’t eat insects!
This is a must be true question, indicated by the question stem: Which one of the following conclusions can be validly drawn from the passage?
Our stimulus opens with the conditional indicator only, which indicates necessity. We learn that for someone to understand Patrick’s irrational behavior it’s required that they be an expert in some branch of psychology. Unfortunately for Patrick, the next sentence, beginning with the conditional indicator no, informs us that if you’re an expert, then you won’t be certain of your ability to solve someone else’s problem. So the only people who will understand Patrick’s problem will be people who won’t be certain about their ability to solve it, right? Wrong. An important inference we should make is that a key detail in that second conditional is that it only applies to someone else’s problem. We need to remember that for all we know Patrick himself could be an expert in some branch of psychology, in which case it would be entirely possible that he understand his own behavioral issues and is certain that he can solve them. Our final sentence tells us that Patrick wants to solve his problems; interesting, but want doesn’t tell us much beyond Patrick’s desire. And that’s all we get! This is a 5 star question, and it is easy to see why. Let’s take a look at the answers:
Answer Choice (A) As always on a must be true question, we should be judging answer choices based on whether they could be false. As noted in our breakdown of the stimulus, we don’t know whether Patrick is an expert in some branch of psychology, so this answer could be false.
Answer Choice (B) Same issue as A but more explicit; we have been given no information about Patrick except that he (i) has a behavioral problem, and (ii) wants to solve it.
Answer Choice (C) Answers A to C all depend on you failing to recognize that we don’t know whether Patrick is an expert. But even if he was, our experts being uncertain rule only applies with reference to someone else, so this still could be false.
Answer Choice (D) We have been told that you need to be an expert in psychology to understand behavioral problems, but we haven’t been told this understanding is required to offer solutions.
Correct Answer Choice (E) Since we know that experts are never certain about solving other’s problems, the only way Charles could be certain is if he wasn’t an expert and therefore couldn’t understand Patrick’s problems.
This is a sufficient assumption question, as the question stem asks: Which one of the following is an assumption that would permit the conclusion above to be properly drawn?
We’re told that every photo must in some ways be true - that stuff in between the commas is science stuff that basically means that because the light of what we capture hits the film. The next sentence begins with a “but” which indicates a potential pivot; the argument goes on to say because of things like Photoshop or angles/posing (cue social media) it doesn’t show the whole trust and is false. Our conclusion comes in and says nothing can ever be proven with photos. First, “nothing” is very strong. Second, being false and proving something are two different, albeit related, ideas. What if you can prove something to be false with an altered photograph by comparing it to what’s actually the case? Let’s link these ideas up with a rule: “If a photograph can be altered to prevent showing the whole truth and is therefore false, then nothing can be proven with it.”
Correct Answer Choice (A) This is correct because it links up our premises with the conclusion and forced our conclusion to be true. While it’s not a perfect paraphrase of our rule, it conveys the same thing.
Answer Choice (B) We’re told that photographs cannot express the whole truth. What does knowing the whole truth have to do with our argument? With our premises and this answer, we cannot force the conclusion.
Answer Choice (C) Being able to figure out whether or not a photograph is truthful does not help push out our conclusion; we still won’t know what is true or false, and this answer choice does not bridge the gap between something being false and figuring out what is not provable.
Answer Choice (D) This does not help justify that nothing can be proven with a photograph. The answer choice adds more information about finding out the truth of the scene of the photograph and then determining what we can use to photograph as evidence. This is more information unrelated to justifying our conclusion.
Answer Choice (E) This would weaken our argument - this is out.
We know this is a sufficient assumption question because of the question stem: “which one… if assumed… would allow [the author] to draw her properly to draw her conclusion…” Interestingly, the conclusion is given to you in the stem. This should help in our formal analysis to figure out what the conclusion is.
Sufficient assumption questions tend to be very formal. We’re looking for a rule that would validate the conclusion, specifically by bridging the premise and conclusion through the rule. Not only are we extrapolating the rule from our argument, but we’re also using that rule to render the argument “valid.” The way to prephrase our answer choice is by tying our premises and conclusion together into a rule: “If [premise] → then [conclusion].”
Our first sentence tells us that an antitheft alarm may stop an attempted theft at night on a crowded street. I’m imagining an incredibly loud siren going off in a middle of a downtown area... I think it’s possible that theft could be prevented with a loud alarm like that.
The next sentence gives an alternative cause for the alarm going off: instead of a thief, it could be a branch or another form of contact.
The third sentence puts aside the causes and says in any of the situations in which the alarm goes off at night, it’s disturbing the sleep of people in the neighborhood. Makes sense - a blaring alarm would definitely disturb my sleep!
Our last sentence, the conclusion which we read in our stem, is: out of consideration for our neighbors, we should deactivate the alarms when parking in crowded city neighborhoods at night.
Why should they?? Protecting a car is probably more important and valuable to its owner than someone else’s sleep, and there doesn’t seem to be a moral code that says people should deactivate their cars if it bothers people’s sleep. On the chance that the car is getting stolen, an alarm would be the best thing to help avoid losing the car! This prescriptive conclusion is assuming that others’ sleep is more important than protecting someone’s car.
What we need is a rule that bridges our premises to our conclusion and validates this prescription. Our premise here is that if the alarm goes off, then people’s sleep is disturbed, and we should be considerate of this. Our conclusion is that owners of these cars should deactivate their alarms. Put them together to make our rule! If people’s sleep is getting disturbed and we should be considerate of this → owners should deactivate car alarms at night.
Answer Choice (A) This would weaken the argument! This is putting the protection of peoples’ cars over peoples’ sleep.
Answer Choice (B) In most cases? What about some cases in which it’s actually a theft? And besides this, the answer choice still does not justify why we should deactivate our alarms. Just because it is a false alarm, it does not validate the argument.
Correct Answer Choice (C) While it’s not a perfect paraphrase of our rule, it gets to the idea that sleep is more important than protecting cars.
Answer Choice (D) Remember, our conclusion is prescriptive. How does saying “people who have alarms are inconsiderate” help our argument? Does this mean they should deactivate their alarms? No – this is out.
Answer Choice (E) We don’t really care about what happens to the alarms during the day, we’re concerned with why people should turn alarms off at night. This is supplemental information that does nothing for our stimulus.
This is a Sufficient Assumption (SA) question and we know this because of the question stem: “conclusion is properly drawn from the premises given if which one of the following is true...”
Sufficient assumption questions tend to be very formal. We’re looking for a rule that would validate the conclusion, specifically by bridging the premise and conclusion through the rule. Not only are we extrapolating the rule from our argument, but we’re also using that rule to render the argument “valid.” The way to prephrase our answer choice is by tying our premises and conclusion together into a rule: “If [premise] → then [conclusion].” Sometimes, a rule is not always helpful. Recognition of what the gap is might be a more useful prephrase.
The first sentence is a comparison between the pull stroke between an S-shaped rake and a straight-handle rake. The S-shaped rake will reduce compression on the spine to 1/5 of what is it with the latter.
The next sentence starts with a “however” which makes me think there is some information that is different or runs contrary to the information presented before in some way (pivoting). Reading on, we learn that on the push stroke, the s-shaped rake exerts 5x more pressure than the straight rake.
In the next sentence, we learned that the compression in the pull/push for the straight rake is not dangerous, but it is above the danger lever for the s-shaped rake. So far all of this is just information/premises. The next sentence begins with “therefore,” and states that straight rakes are better than s-shaped rakes for minimizing the risk of spinal injury. This is our conclusion.
What is the gap here? Well, jumping from compression stress injuries on the spine to all injuries on the spine. And also, the statistics of risk are equal: X being 5 times Y and Y being 1/5 of X is equal. Why should we prefer a straight-handled rake if the risk of injury for pulling in one and pushing in the other is the same? Our rule needs to relate stress caused by pushing (because that’s the one where s-shaped rakes are worse) to factors associated with all spinal injuries when raking. Not only that, but it needs to explicitly say that the two go hand in hand, or compression related to the push (and not pull) stroke is one of the most important factors in all spinal injuries caused by raking.
Correct Answer Choice (A) This answer choice is relating compression from pushing and spinal injuries in a causal relationship by saying that compression stress from pushing rakes is the only cause of spinal injuries from raking. So, of all the injuries that happen with raking, spinal injuries are only caused by compression stress from pushing the rake, which means that we can conclude that straight rakes are better for minimizing spinal injuries in general.
Answer Choice (B) This is not the correct answer. It’s not relevant to making our conclusion valid – sure, a gardener can still get spinal injuries by using even a straight-handled rake. If we plug this back into our stimulus, it doesn’t really do anything.
Answer Choice (C) This is describing what is happening with the redesign’s flaw. If this was a principle question, this would be a great answer choice. However, this is an SA question and our conclusion has nothing to do with a redesign having no gain in efficiency. We’re making a judgment claim on which rake is better as it relates to a specific category of injuries.
Answer Choice (D) This is basically saying that some strokes have to be pull strokes, which means that there is some risk of compression injury with a straight handle. This attempts to weaken our answer choice but fails because some risk while raking is compatible with our conclusion (it’s about lowering risk, not eliminating it).
Answer Choice (E) This is pointless to our argument. We’re trying to say that one is better than the other, not introduce a third option.