Editorial: A proposed new law would limit elementary school class sizes to a maximum of 20 students. Most parents support this measure and argue that making classes smaller allows teachers to devote more time to each student, with the result that students become more engaged in the learning process. However, researchers who conducted a recent study conclude from their results that this reasoning is questionable. The researchers studied schools that had undergone recent reductions in class size, and found that despite an increase in the amount of time teachers spent individually with students, the students’ average grades were unchanged.

Which one of the following is an assumption required by the researchers’ argument?

Company spokesperson: In lieu of redesigning our plants, our company recently launched an environmental protection campaign to buy and dispose of old cars, which are generally highly polluting. Our plants account for just 4 percent of the local air pollution, while automobiles that predate 1980 account for 30 percent. Clearly, we will reduce air pollution more by buying old cars than we would by redesigning our plants.

Which one of the following, if true, most seriously weakens the company spokesperson’s argument?

Historian: Radio drama requires its listeners to think about what they hear, picturing for themselves such dramatic elements as characters’ physical appearances and spatial relationships. Hence, while earlier generations, for whom radio drama was the dominant form of popular entertainment, regularly exercised their imaginations, today’s generation of television viewers do so less frequently.

Which one of the following is an assumption required by the historian’s argument?

Newspaper article: People who take vitamin C supplements tend to be healthier than average. This was shown by a study investigating the relationship between high doses of vitamin C and heart disease, which showed that people who regularly consume high doses of vitamin C supplements have a significantly lower than average risk of heart disease.

Which one of the following, if true, would most weaken the argument in the newspaper article?

Mammals cannot digest cellulose and therefore cannot directly obtain glucose from wood. Mushrooms can, however; and some mushrooms use cellulose to make highly branched polymers, the branches of which are a form of glucose called beta-glucans. Beta-glucan extracts from various types of mushrooms slow, reverse, or prevent the growth of cancerous tumors in mammals, and the antitumor activity of beta-glucans increases as the degree of branching increases. These extracts prevent tumor growth not by killing cancer cells directly but by increasing immune-cell activity.

Which one of the following is most strongly supported by the information above?

In the past, when there was no highway speed limit, the highway accident rate increased yearly, peaking a decade ago. At that time, the speed limit on highways was set at 90 kilometers per hour (kph) (55 miles per hour). Every year since the introduction of the highway speed limit, the highway accident rate has been at least 15 percent lower than that of its peak rate. Thus, setting the highway speed limit at 90 kph (55 mph) has reduced the highway accident rate by at least 15 percent.

Which one of the following, if true, most seriously weakens the argument?

A recent study of major motion pictures revealed that the vast majority of their plots were simply variations on plots that had been used many times before. Despite this fact, many people enjoy seeing several new movies each year.

Each of the following, if true, would contribute to an explanation of the apparent discrepancy in the information above EXCEPT:

Psychologist: Identical twins are virtually the same genetically. Moreover, according to some studies, identical twins separated at birth and brought up in vastly different environments show a strong tendency to report similar ethical beliefs, dress in the same way, and have similar careers. Thus, many of our inclinations must be genetic in origin, and not subject to environmental influences.

Which one of the following, if true, would most weaken the psychologist’s argument?

After the rush-hour speed limit on the British M25 motorway was lowered from 70 miles per hour (115 kilometers per hour) to 50 miles per hour (80 kilometers per hour), rush-hour travel times decreased by approximately 15 percent.

Which one of the following, if true, most helps to explain the decrease in travel times described above?

Technologically, it is already possible to produce non-polluting cars that burn hydrogen rather than gasoline. But the national system of fuel stations that would be needed to provide the hydrogen fuel for such cars does not yet exist. However, this infrastructure is likely to appear and grow rapidly. A century ago no fuel-distribution infrastructure existed for gasoline powered vehicles, yet it quickly developed in response to consumer demand.

Which one of the following most accurately expresses the conclusion drawn in the argument?

Administrators of educational institutions are enthusiastic about the educational use of computers because they believe that it will enable schools to teach far more courses with far fewer teachers than traditional methods allow. Many teachers fear computers for the same reason. But this reason is mistaken. Computerized instruction requires more, not less, time of instructors, which indicates that any reduction in the number of teachers would require an accompanying reduction in courses offered.

The statement that the educational use of computers enables schools to teach far more courses with far fewer teachers figures in the argument in which one of the following ways?

Chef: This mussel recipe’s first step is to sprinkle the live mussels with cornmeal. The cornmeal is used to clean them out: they take the cornmeal in and eject the sand that they contain. But I can skip this step, because the mussels available at seafood markets are farm raised and therefore do not contain sand.

Which one of the following is an assumption required by the chef’s argument?