Scientists examined diamonds that were formed on Earth about 2.9 billion years ago. These diamonds had a higher-than-normal concentration of sulfur-33. This concentration can be explained only by certain chemical reactions that are stimulated by ultraviolet light. If there had been more than a trace of oxygen in Earth’s atmosphere 2.9 billion years ago, then not enough ultraviolet light would have reached Earth’s surface to stimulate the chemical reactions.

Summary
Scientists examined diamonds formed 2.9 billion years ago and concluded these diamonds had higher-than-normal concentrations of sulfur-33. The only way this concentration occurs is from a chemical reaction triggered by ultraviolet light. If there was more than a trace of oxygen in the atmosphere 2.9 billion years ago, then not enough ultraviolet light would be present to cause the chemical reaction.

Strongly Supported Conclusions
2.9 billion years ago the atmosphere had at most very little oxygen.

A
Most diamonds with higher-than-normal concentrations of sulfur-33 were formed at least 2.9 billion years ago.
This answer is unsupported. We don’t know if this is true of most diamonds with this concentration. We only know from the stimulus that there are at least a few of them formed 2.9 billion years ago.
B
Ultraviolet light causes the oxygen in Earth’s atmosphere to react chemically with sulfur-33.
This answer is unsupported. We don’t know whether the oxygen is specifically reacting with sulfur-33. We only know from the stimulus that a “certain chemical reaction” occurs when stimulated by ultraviolet light.
C
Earth’s atmosphere contained very little, if any, oxygen 2.9 billion years ago.
This answer is strongly supported. This answer explains why the diamonds in the stimulus have higher than normal concentrations of sulfur-33.
D
Sulfur-33 is rarely found in diamonds that were formed more recently than 2.9 billion years ago.
This answer is unsupported. We don’t know anything about more recently formed diamonds from the stimulus. The stimulus is strictly limited to the diamonds scientists are examining from 2.9 billion years ago.
E
The formation of diamonds occurs only in the presence of ultraviolet light.
This answer is unsupported. We don’t know from the stimulus under what conditions diamonds are formed generally.

3 comments

When a patient failed to respond to prescribed medication, the doctor hypothesized that the dosage was insufficient. The doctor first advised doubling the dosage, but the patient’s symptoms remained. It was then learned that the patient regularly drank an herbal beverage that often inhibits the medication’s effect. The doctor then advised the patient to resume the initial dosage and stop drinking the beverage. The patient complied, but still showed no change. Finally, the doctor advised the patient to double the dosage and not drink the beverage. The patient’s symptoms disappeared. Hence, the doctor’s initial hypothesis was correct.

Summarize Argument: Phenomenon-Hypothesis

The author concludes that the doctor’s initial hypothesis—that the original dosage was too low—was correct. She supports this by describing three sets of recommendations made by the doctor:

Double the dosage. (Symptoms remained.)

Return to original dosage but stop drinking a beverage that inhibits the medication. (Symptoms remained.)

Double the dosage again, keep avoiding the beverage. (Symptoms disappeared!)

Describe Method of Reasoning

The second set of recommendations lends support to the initial hypothesis that the dosage was too by eliminating an alternative hypothesis. Since the patient’s symptoms remained after this set of recommendations, it’s likely that the beverage wasn’t the sole cause of the original dosage’s ineffectiveness.

A
They establish that the doctor’s concerns about the healthfulness of the beverage were well founded.

Actually, when the patient stopped drinking the beverage and returned to the original dosage, his symptoms still remained. So the results of the second set of recommendations don’t yet establish that the doctor’s concerns about the beverage were well founded.

B
They make it less plausible that the beverage actually contributed to the ineffectiveness of the prescribed medication.

The patient’s symptoms remained after quitting the beverage and returning to the original dosage. Even if the beverage is a contributing factor, these results suggest that the original dosage is indeed too low, whether the patient is drinking the beverage or not.

C
They give evidence that the beverage was responsible for the ineffectiveness of the prescribed medication.

We don't know yet if the beverage caused the medicine to be ineffective. In fact, because the symptoms remained, we now know that the beverage alone wasn’t entirely responsible. Also, if (C) were true, it would weaken the original hypothesis; we need an answer that supports it.

D
They suggest that the beverage was not the only cause of the ineffectiveness of the prescribed dosage.

Since the symptoms remained after stopping the beverage, it shows the beverage wasn't the only cause of the dosage's ineffectiveness. This supports the hypothesis that the dosage was too low by eliminating the alternative hypothesis that the beverage alone was responsible.

E
They rule out the possibility that the doctor had initially prescribed the wrong medication for the patient’s ailments.

The results of the second set of recommendations don’t rule out this possibility because it’s still unclear whether a higher dosage of the original medication will help the patient or not.


19 comments

Although most builders do not consider the experimental building material papercrete to be a promising material for large-scale construction, those who regularly work with it, primarily on small-scale projects, think otherwise. Since those who regularly use papercrete are familiar with the properties of the material, it is likely that papercrete is indeed promising for large-scale construction.

Summarize Argument
Contrary to the opinion of most builders, the author concludes that it’s likely papercrete is promising for large-scale construction. This is because those who regularly work with papercrete think it’s promising, and those people are familiar with the properties of the material.

Identify and Describe Flaw
The author cites to the familarity with papercrete properties among those who regularly work with papercrete. This familiarity is why the author favors their opinion over most builders. But this assumes that most builders do not have familarity with papercrete properties. If they do, then familiarity with papercrete is no longer a basis to give weight to one opinion over the other.

A
confuses what is promising for small-scale construction with what is promising for large-scale construction
The author doesn’t assume that what’s promising for small-scale must also be promising for large-scale. He relies on the opinion of those who regularly work with papercrete. Also, we don’t know that papercrete actually is promising for small-scale.
B
presumes that what the majority of builders thinks is promising must in fact be promising
Most builders don’t consider papercrete promising for large-scale construction. So the author is actually going against majority opinion.
C
equivocates between two different meanings of the term “promising”
There’s no indication “promising” means two different things in the argument. “Promising” uses the ordinary dictionary definition for this context (definition = showing signs of future success).
D
does not consider the views of the builders who have the most experience working with the material
If we assume those who use papercrete regularly have the most experience, the author does consider their views. If we don’t know whether they have the most experience, then (D) is inaccurate because we don’t know whether the author ignored the views of the most experienced.
E
fails to consider that most builders might not regularly use papercrete precisely because they are familiar with its properties
(E) points out that the builders who don’t think papercrete is promising might be familiar with papercrete’s properties. So, pointing to the familiarity of those who do think papercrete is promising is no longer a reason to rely on their opinion over the opinion of most builders.

34 comments

Drama critic: There were many interesting plays written last year. Surely some will gain widespread popularity for at least a few years, and some will even receive high critical acclaim, but none will be popular several centuries from now. The only plays that continue to be performed regularly over many decades and centuries are those that skillfully explore human nature, and none of the plays written last year examine human nature in a particularly skillful way.

Summary
The author concludes that none of the many interesting plays written last year will be popular several centuries from now.
Why? Because of the following:
In order for a play to be performed regularly over many decades and centuries, it must skillfully explore human nature.
The plays written last year (including the interesting ones) do not skillfully explore human nature.

Notable Assumptions
Notice that the conclusion bring up a new concept — not being popular several centuries from now. The premises don’t say anything about what will be unpopular several centuries from now, so we know the author must assume something about this concept.
To go further, we can anticipate a more specific connection to get from the premises to the conclusion. We know from the premises that the interesting plays written last year won’t be performed regularly over the coming decades and centuries (because they don’t examine human nature in a particularly skillful way). The author assumes that if the plays aren’t performed regularly over the coming decades and centuries, then they won’t be popular several centuries from now. Or, in other words, in order to be popular several centuries from now, they must be performed regularly.

A
No play will be popular several centuries from now unless it continues to be performed regularly during the intervening time.
This is the necessary link between the premises and the conclusion. If this were not true — if plays could be popular centuries from now even if they weren’t regularly performed — then the premises wouldn’t prove that the plays won’t be popular centuries from now.
B
For a play to deserve high critical acclaim it must be popular for more than just a few years.
The author’s reasoning has nothing to do with critical acclaim. The author mentioned critical acclaim in the beginning, but that was simply part of context and plays no role in the premise to conclusion structure of the author’s argument.
C
There were no plays written last year that the drama critic has neither read nor seen performed.
Not necessary, because the critic doesn’t have to have seen or read all the plays. We know as a premise that none of the plays written last year examine human nature in a skillful way. The critic doesn’t need to have seen or read all plays in order for that premise to be true.
D
If a play does not skillfully explore human nature, it will not receive critical acclaim.
The author’s reasoning has nothing to do with critical acclaim. The author mentioned critical acclaim in the beginning, but that was simply part of context and plays no role in the premise to conclusion structure of the author’s argument.
E
Any play that skillfully examines human nature will be performed regularly over the centuries.
The author’s argument concerns plays that do NOT skillfully examine human nature and what will happen to them. So the author doesn’t need to assume anything about what will happen to plays that DO skillfully examine human nature.

51 comments

Annie: Our university libraries have been sadly neglected. Few new books have been purchased during the last decade, and most of the older books are damaged. The university’s administrators should admit that their library policies have been in error and should remedy this situation in the fastest way possible, which is to charge students a library fee and use the funds for library improvements.

Matilda: The current poor condition of the university libraries is the fault of the library officials, not the students. Students should not have to pay for the mistakes of careless library administrators.

Speaker 1 Summary
Annie concludes that the university’s administrators should admit that their policies have been in error, should charge students a library fee, and should use the funds for library improvements. This is based on the fact that there have been few books purchased in the last decade, most older books are damaged, and charging students a fee is the fastest way possible to address these problems.

Speaker 2 Summary
Matilda concludes that students should not have to pay a library fee. This is because the problems with the library are the fault of library officials.

Objective
We’re looking for a disagreement. The speakers disagree about whether students should be charged a fee to improve the library.

A
library administrators are to blame for the poor condition of the university libraries
Not a point of disagreement. Annie blames university administrators, who are reasonably considered the same as the library officials Matilda blames. Even if they’re not, Annie might still blame both library officials and university administrators.
B
library improvements could be most quickly effected through charging students additional fees
Matilda expresses no opinion. She might agree with Annie that a student fee is the fastest way to improve the library.
C
students will ultimately benefit from the library improvements that could be funded by additional student fees
Matilda expresses no opinion. She doesn’t suggest any opinion about the results of student fees or of library improvements. In addition, it’s reasonable to think Matilda agrees that library improvements would help users of the library, such as students.
D
those not responsible for the current condition of the libraries should bear the cost for remedying it
This is a point of disagreement. Matilda thinks students should not be responsible for improvements. Annie believes students should be charged a fee for library improvements. She doesn’t explicitly say students aren’t responsible, but she blames administrators’ policies.
E
funds for library improvements could be raised without additional student fees
Not a point of disagreement. Matilda doesn’t discuss whether the university can get funds without a student fee.

3 comments

For years, a rare variety of camel was endangered because much of its habitat was used as a weapons testing range. After the testing range closed, however, the population of these camels began falling even more quickly.

"Surprising" Phenomenon
Why did the population of camels fall more quickly after a weapons testing range in its habitat was closed, even though the presence of the range endangered the camels?

Objective
The correct answer should suggest a potential difference between conditions after the range was closed and before it was closed, and this difference would lead to a greater threat to camels after the range was closed.

A
The weapons tests had kept wildlife poachers out of the testing range.
This suggests that the threat of wildlife poaching (which would tend to kill camels) was greater after the range was closed. This increased threat could have outweighed whatever benefits the camels saw from a reduction in weapons testing at the range.
B
Weapons testing in the range did more harm to the camels in the first years of the testing than in later years.
Even if the range was less harmful later, we’d still expect the closing of the range to completely remove any harm from weapons testing. So, we still wouldn’t expect the camel population to decrease more quickly after the closing.
C
Because of unexploded bombs, the land within the testing range was still somewhat dangerous after the range closed down.
We want to explain why the camel population began to fall more quickly after closing. We’re not just trying to explain why the benefits to the camels weren’t as great as anticipated. This doesn’t tell me why things got worse for the camels after closing.
D
The camels had to overcome two different outbreaks of disease during the time the testing range was in operation.
This doesn’t suggest any difference between before and after the closing. Even if you read this as suggesting camels didn’t face as many disease outbreaks after the closing, that would make it more difficult to explain the faster drop in camel population after closing.
E
The weapons tests were most harmful to the camels in years when food was scarce.
This doesn’t suggest any difference between before and after closing. We’d still expect overall harm to camels to go down after closing.

14 comments

Planting peach trees on their farm makes more sense for the Johnsons than planting apricot trees. Although fresh, locally grown apricots are very popular in this area, the same is true of peaches. However, individual peach trees cost much less to purchase and plant than do apricot trees, and peach trees also begin bearing fruit at a much younger age.

Summarize Argument

The author concludes that the Johnsons should plant peach trees rather than apricot trees. She supports this by saying that, while both are popular, peach trees are less expensive than apricot trees and they start producing fruit at a much younger age.

Notable Assumptions

The author assumes that planting cheaper trees will increase the Johnsons’ profit without considering other factors, like the cost of maintenance or the price of peaches versus apricots.

She also assumes that, because peach trees produce fruit at a younger age, they will produce more fruit over time. She doesn’t consider whether peach trees stop producing fruit at a young age, or whether they simply produce far less fruit overall.

She also assumes that these are the most important factors in the Johnsons’ decision, overlooking any other factors that might make apricots a better option.

A
Fresh, locally grown apricots sell at a much higher price than do fresh, locally grown peaches.

This weakens the argument by showing that one of the author's assumptions is false. She assumes that cheaper trees will lead to more income for the farm, but (A) points out that apricots, which sell for a higher price, could actually generate more income than peaches long term.

B
Apricot trees tend to stop being productive at a younger age than do peach trees.

This strengthens the argument. If apricots stop being productive at a younger age, it might make more sense for the Johnsons to plant peaches instead.

C
It costs as much to water and fertilize peach trees as it does to water and fertilize apricot trees.

Like (B), this slightly strengthens the argument. If water and fertilizer costs are the same but peach trees are less expensive to buy and plant, it might make more sense for the Johnsons to plant peaches instead of apricots.

D
The market for fresh, locally grown apricots has grown in recent years as awareness of the health benefits of eating fresh fruit has increased.

(D) wants us to assume that the market for apricots has grown more than the market for peaches, but we don’t know this. Since “awareness of the health benefits of eating fresh fruit has increased,” it’s very possible that the market for peaches has grown just as much or more.

E
Peach production has decreased dramatically over the last several years.

This doesn’t address the author’s argument or assumptions. If peach production has decreased, should they plant peaches to fill this gap in production? Or should they avoid planting them due to other factors affecting production? We simply don’t know.


27 comments

A person reading a new book for pleasure is like a tourist traveling to a new place. The reader reads, just as the tourist travels, to enlarge understanding rather than simply to acquire information. Thus, it is better to read fewer books and spend more time on each rather than to quickly read as many as one can, just as it is better to travel to fewer places and spend more time in each rather than to spend a small amount of time in many different places.

Summarize Argument
The author concludes that it’s better to read fewer books and spend more time on each, rather than reading as many as possible. As support, she draws an analogy, saying that it’s better to travel to fewer places and spend more time in each, rather than spending a little time in many places. She notes that reading, like traveling, is about deepening understanding, instead of just gaining new information.

Notable Assumptions
In order to draw an analogy between reading and traveling, the author assumes that there are no relevant differences between the two. She also assumes that spending more time in one place leads to a better understanding of that place than spending less time there does.

A
Tourists typically learn something about the places they visit even when they are there only to relax.
Irrelevant. This fails to address whether tourists deepen their understanding of a place when they spend more time there. The author focuses on how long tourists are in a place, not why they are there.
B
Tourists gain much more understanding of a place once they have spent several days at that place than they do in their first few days there.
If tourists gain more understanding of a place once they’ve spent several days there and reading is like traveling, this suggests that readers gain more understanding by spending more time reading each book.
C
Many people report that they can learn far more about a place by visiting it than they can by reading about it.
Irrelevant. This fails to address whether tourists deepen their understanding of a place when they spend more time there. The author uses reading and traveling as two different but analogous activities, both of which deepen understanding. Like (D), (C) mixes them together.
D
Tourists who have read about a place beforehand tend to stay longer in that place.
Irrelevant. This fails to address whether tourists deepen their understanding of a place when they spend more time there. The author uses reading and traveling as two different but analogous activities, both of which deepen understanding. Like (C), (D) mixes them together.
E
Some tourists are unconcerned about gaining information about a place other than what is necessary for their immediate enjoyment.
Irrelevant. This fails to address whether tourists deepen their understanding of a place when they spend more time there. Also, the author already said that people travel “to enlarge understanding rather than simply to acquire information.”

4 comments

One way to furnish a living room is with modular furniture. Instead of buying a standard sofa, for example, one can buy a left end, a right end, and a middle piece that can be combined to create an L-shaped sofa. Modular furniture, however, is far more expensive than standard furniture. On average, a three-piece modular sofa costs almost twice as much as a standard sofa of comparable size and quality.

"Surprising" Phenomenon
Why is modular furniture more expensive than standard furniture, even if it’s of comparable size and quality?

Objective
This is an EXCEPT question. Four wrong answers will differentiate modular furniture from standard furniture in a way that could lead modular furniture to be more expensive.

A
Modular furniture, unlike standard furniture, is not mass-produced.
This is a difference between modular and standard furniture that could lead to modular furniture being more expensive. Something mass-produced might cost less to make, which means lower prices for consumers.
B
The consumer demand for sofas sometimes increases more quickly than the supply.
This doesn’t differentiate modular furniture from standard furniture. We still don’t have any reason to think modular furniture would be more expensive.
C
The most fashionable designers tend to use modular furniture designs.
This suggests a difference between modular furniture and standard furniture. Perhaps modular furniture might be more expensive because it is more fashionable or associated with more fashionable designers.
D
Because modular furniture pieces are custom ordered, they are never put on sale.
This is a difference between modular furniture and standard furniture that could explain why modular furniture is more expensive. All else equal, something on sale is likely to be less expensive than something not on sale.
E
Modular sofas, on average, have a greater area of upholstered surfaces than do standard sofas.
This is a difference between modular furniture and standard furniture that could explain why modulfar furniture is more expensive. More upholstered surfaces might increase production costs, which could lead to higher prices for consumers.

23 comments

The hormone testosterone protects brain cells from injury and reduces levels of the protein beta-amyloid in the brain. Beta-amyloid causally contributes to Alzheimer’s disease, and people whose brain cells are susceptible to injury are probably more susceptible to Alzheimer’s disease. So there is reason to think that _______.

Summary
Testosterone protects brain cells from injury. Testosterone reduces levels of beta-amyloid, a protein, in the brain. Beta-amyloid has a causal relationship with Alzheimer’s disease. People whose brain cells are more susceptible to injury are probably more likely to get Alzheimer’s.

Strongly Supported Conclusions
Testosterone protects against Alzheimer’s by reducing the likelihood of brain cell injury. A decline in testosterone increases the risk of Alzheimer’s disease.

A
anyone whose brain cells are susceptible to injury will eventually develop Alzheimer’s disease
This is unsupported because we don’t know that being susceptible to brain cell injury is a sufficient condition for Alzheimer’s disease. We only know that people susceptible to brain cell injury are probably more susceptible to Alzheimer’s disease.
B
whether a person develops Alzheimer’s disease is dependent entirely on the level of beta-amyloid in his or her brain
This is unsupported because the stimulus leaves open the possibility that other factors besides beta-amyloid influence Alzheimer’s development.
C
Alzheimer’s disease leads to a reduction in testosterone level
This is unsupported because the causation may be the other way around. Reductions in testosterone may lead to Alzheimer’s disease.
D
only people with Alzheimer’s disease are at risk for injury to brain cells
This is unsupported because people susceptible to brain cell injury may have low testosterone with no Alzheimer’s disease.
E
a decline in testosterone level puts one at increased risk for Alzheimer’s disease
This is strongly supported because a decline in testosterone leads to increased susceptibility to brain injury, which probably makes someone more likely to develop Alzheimer’s disease.

2 comments