Summarize Argument
The author concludes that people who lived a century ago probably read a lot more than we read today. As support for this theory, the author cites the fact that those who lived a century ago had very few diversions to amuse them.
Notable Assumptions
The author is assuming that a lack of diversions would lead to people choosing to read more, as opposed to some other activity that could provide amusement. The author is also assuming that enough people were literate a century ago to read “much more” than people read today. Additionally, the author is assuming that people had enough free time to read at a similar level to the amount of time that people spend reading today.
A
Many of the books published a century ago were of low literary quality.
Just because books are of low literary quality does not mean that people won’t be reading them. Also, (A) does not compare literary quality of books a century ago with literary quality of books today. It could be that many books published today are also of low literary quality.
B
On average, people who lived a century ago had considerably less leisure time than we do today.
(B) gives a reason that, even though people a century ago had fewer sources of diversion, they may not have read much more than we do today. Even if people today have more options for diversion, if we have more time to fill, we could be reading more than people a century ago.
C
The number of books sold today is larger than it was a century ago.
More total book sales does not necessarily indicate more time spent reading per capita. Also, the population today is much higher than it was a century ago, which would account for the increase in book sales without an increase in time that people spend reading.
D
On the average, books today cost slightly less in relation to other goods than they did a century ago.
The argument connects available diversions to time spent reading, so book cost is out of the scope of the argument. Also, (D) compares book costs with the cost of goods in general, not the cost of other sources of amusement. Books could have been a cheap source of amusement.
E
One of the popular diversions of a century ago was horse racing.
The author only claims that there were fewer diversions a century ago, not that reading was the only diversion. Also, (E) does not make a comparison between conditions a century ago and conditions today.
Summarize Argument
The advertisement concludes that customers are assured a fair price on diamonds at Gem World. This is because all diamonds sold at Gem World are certified in writing.
Notable Assumptions
The advertisement assumes that diamonds that are certified in writing are assessed by someone other than the person selling them. Moreover, the advertisement assumes that whoever sells the diamond at Gem World isn’t inclined to lie about the diamond’s quality. If the salesperson wasn’t obliged to provide the written certification, then they may well lie about the quality of the diamond.
A
Many jewelry stores other than Gem World also provide written certification of the quality of their diamonds.
The advertisement doesn’t say Gem World is alone in their practice. It simply says Gem World is preferable from a customer standpoint to most jewelry stores.
B
The certifications of diamonds at Gem World are written by people with years of experience in appraising gems.
This seems to strengthen the argument, but we have no idea if those people are associated with Gem World. If they get some commission on each diamond, they might be inclined to pretend the diamonds are of higher quality than they really are.
C
The diamonds sold at Gem World are generally of higher quality than those sold at other jewelry stores.
We don’t care how high-quality the gems are. We care if Gem World is in fact honest about the quality of each diamond.
D
The diamond market is so volatile that prices of the most expensive diamonds can change by hundreds of dollars from one day to the next.
We don’t care about the exact price. We care if Gem World is in fact honest about the quality of each diamond.
E
The written certifications of diamonds at Gem World are provided by an independent company of gem specialists.
The diamonds are appraised by an independent company that has no stake in how much each diamond sells for. Thus, we can accept that their written certifications probably aren’t biased in favor of Gem World’s business interests.
Summary
Newtonian physics dominated science for over two centuries and became one of the most highly accepted theories in the history of science. Nevertheless, Einstein’s theories later came to show the limits of Newtonian physics and surpassed the Newtonian view in the early 1900s. Einstein’s theories have so far enjoyed wide success.
Notable Valid Inferences
A scientific theory’s widespread acceptance is no guarantee that the theory will be accepted forever.
A
The history of physics is characterized by a pattern of one successful theory subsequently surpassed by another.
Could be false. The stimulus only gives us two examples of scientific theories, one of which subsequently surpassed the other. This doesn’t necessarily establish a pattern, it could be that Newtonian physics and Einstein’s theories are the only examples of this occurring.
B
Long-standing success or substantiation of a theory of physics is no guarantee that the theory will continue to be dominant indefinitely.
Must be true. We know that Einstein’s theories eventually surpasses Newtonian physics despite Newtonian physics dominating science for over two centuries.
C
Every theory of physics, no matter how successful, is eventually surpassed by one that is more successful.
Could be false. The stimulus only gives us two examples of scientific theories, one of which subsequently surpassed the other. This doesn’t necessarily mean that every theory is eventually surpassed. It could be that Einstein surpassing Newtonian physics is a unique occurrence.
D
Once a theory of physics is accepted, it will remain dominant for centuries.
Could be false. We only know that Newtonian physics was dominant for centuries. It could be the case that Newtonian physics is unique, and that no other theory of physics has been accepted for centuries.
E
If a long-accepted theory of physics is surpassed, it must be surpassed by a theory that is equally successful.
Could be false. We know that Einstein’s theories surpassed Newtonian physics, but we cannot assume Einstein’s theories are equally successful. Newtonian physics dominated for over two centuries, and Einstein’s theories have not existed for as long.
Summary
Every person who participated in the town’s annual spring cleanup received a community recognition certificate. However, there are some spring cleanup participants who are not active in the town’s artistic circles because the spring cleanup took place at the same time as the downtown arts fair.
Notable Valid Inferences
Some people who received community recognition certificates are not active in the town’s artistic circles.
A
Some of the persons who are active in the town’s artistic circles received community recognition certificates.
Could be false. As shown in our diagram, our conditions are limited to persons who are not active in the town’s artistic circles. We cannot infer anything about people who are active in the town’s artistic circles.
B
Not all of those who received community recognition certificates are active in the town’s artistic circles.
Must be true. As shown below, we can always infer a “some” statement between conditions that branch off from a sufficient condition in common. 
C
No participants in the downtown arts fair received community recognition certificates.
Could be false. We know that the arts fair and the spring cleanup took place at the same time, but we cannot assume that it is impossible for a person to participate in both events.
D
No person who received a community recognition certificate has not participated in the spring cleanup.
Could be false. This answer choice confuses sufficiency for necessity. It is possible that a person received a recognition certificate without participating in the cleanup. A necessary condition can always occur without the sufficient condition.
E
Persons who are active in the town’s artistic circles are not concerned with the town’s environment.
Could be false. As shown on our diagram, we have no conditions relevant to a person’s concern with the environment. Moreover, we cannot assume that people who didn’t participate in the cleanup are not concerned with the environment.
Summary
After the Cold War, international relations between allied nations became more difficult. Leaders of previously allied nations were required conduct tactful economic negotiations for the purpose of not triggering tensions that were previously overlooked.
Strongly Supported Conclusions
Bonds between nations are strengthened by a common enemy, and this bond enables nations to overlook otherwise problematic economic tensions.
A
International economic competition is a greater cause of tension than is international military competition.
This answer is unsupported. We don’t know from the stimulus whether military competition was a cause of tension between nations.
B
Bonds between allies are stronger when they derive from fear of a common enemy than when they derive from common economic goals.
This answer is unsupported. We don’t know anything about bonds derived from common economic goals from the stimulus.
C
When there is a military commitment between countries, fundamental agreement between them on economic matters is more easily reached.
This answer is unsupported. We don’t know from the stimulus whether economic agreement was more easily reached between allied nations. We only know that these bonds led nations to overlook economic tensions.
D
Economic matters are considered unimportant during periods of actual or threatened war.
This answer is unsupported. We don’t know whether economic matters were considered unimportant. We only know that economic tensions may have been overlooked.
E
A common enemy contributes to a strengthened bond between nations, enabling them to ignore economic tensions that would otherwise be problematic.
This answer is strongly supported. This principle explains why, after the Cold War, previously allied nations were required to conduct tactful economic negotiations. The nations’ allegiance allowed them to overlook economic tensions between themselves.