Letter to the editor: If the water level in the Searle River Delta continues to drop, the rising sea level will make the water saltier and less suitable for drinking. Currently, 40 percent of the water from upstream tributaries is diverted to neighboring areas. To keep the delta’s water level from dropping any further, we should end all current diversions from the upstream tributaries.

Neighboring water utilities are likely to see higher costs and diminished water supplies, but these costs are necessary to preserve the delta.

Which of the following would, if true, indicate a serious potential weakness of the suggested plan of action?

A company’s personnel director surveyed employees about their satisfaction with the company’s system for awarding employee performance ratings. The survey data indicated that employees who received high ratings were very satisfied with the system. The personnel director concluded from these data that the company’s best-performing employees liked the system.

The personnel director’s conclusion assumes which of the following?

A new handheld device purports to determine the severity of concussions by reading the brain’s electrical signals and comparing them to a database of 15,000 scans compiled at a brain research lab. The device is intended to help doctors decide whether an athlete who has received a blow to the head during a competition should be sent back into the game.

Which of the following would it be most useful to establish in order to evaluate the effectiveness of the device for its intended purpose?

Exports of United States wood pulp will rise considerably during this year. The reason for the rise is that the falling value of the dollar will make it cheaper for paper manufacturers in Japan and Western Europe to buy American wood pulp than to get it from any other source.

Which of the following is an assumption made in drawing the conclusion above?

Distressed by his own personal tragedies, the Roman philosopher Cicero once asked himself whether a wise person should try to achieve the Stoic ideal of complete emotionlessness. Cicero reasoned that, however desirable the goal may be, a wise person could never attain it, since emotions are not simply irrational urges. They are, rather, a product of one’s estimate of the goodness and badness of the events, people, and actions one witnesses.

Which of the following is an assumption required by Cicero’s reasoning?

Although elementary school children have traditionally received considerable instruction in creating visual art, there has been no such instruction in music. Consequently, in contrast to the situation for visual art, most people as adults do not recognize the artistic intentions of composers. To remedy this situation, a few educators now recommend teaching elementary school students to compose music.

Which of the following, if true, is the strongest basis for arguing that implementation of the recommendation will not lead to the desired result?

Scientist: A greenhouse gas, for example, carbon dioxide, forms a transparent layer that traps solar heat beneath it in the earth’s atmosphere. Atmospheric levels of carbon dioxide are currently increasing, causing the climate to warm—an effect that is predicted by at least one computer model of the greenhouse effect. But the warming that has occurred is a great deal less than what would be expected based on the model. Therefore, 

Which of the following most logically completes the scientist’s argument?

First discovered several years ago in North American lakes and rivers, the northern snakehead is a nonnative fish with no local predators. To keep the northern snakehead ’s population from growing, for the past three years wildlife officials have been paying recreational fishers for each northern snakehead they catch. In this way, the officials hope to stop the northern snakeheads from eliminating rare native fish species.

To evaluate the likelihood that the wildlife officials’ plan will succeed, it would be most useful to determine which of the following?

Researchers conditioned a group of flies to associate a particular odor with a weak electric shock. Twenty-four and forty-eight hours later the researchers conducted tests on the flies, both individually and in groups, to determine whether the flies retained the conditioning. When tested individually, the flies were significantly less likely to avoid areas marked with the odor. The researchers hypothesized that in the presence of the odor, a fly that retains the conditioned association gives off an alarm signal that arouses the attention of any surrounding flies, retriggering the association in them and thereby causing them to avoid the odor.

The researchers’ hypothesis requires which of the following assumptions?

Pharmaceutical companies spend more than ever on research and development; yet the number of new drugs patented each year has dropped since 1963. At the same time, profits— at constant 1963 dollars—for the industry as a whole have been steadily increasing.

Which of the following, if true, is the single factor most likely to explain, at least in part, the three trends mentioned above for money spent, drugs patented, and profits made?