Several thousand years ago, people in what is now North America began to grow corn, which grows faster and produces more food per unit of land than do the grains these people had grown previously. Corn is less nutritious than those other grains, however, and soon after these people established corn as their staple grain they began having nutrition-related health problems. Yet the people continued to grow corn as their staple grain, although they could have returned to growing the more nutritious grains.

Which one of the following, if true, most helps to explain why the people mentioned continued to grow corn as their staple grain crop?

The law of the city of Weston regarding contributions to mayoral campaigns is as follows: all contributions to these campaigns in excess of $100 made by nonresidents of Weston who are not former residents of Weston must be registered with the city council. Brimley’s mayoral campaign clearly complied with this law since it accepted contributions only from residents and former residents of Weston.

If all the statements above are true, which one of the following statements must be true?

In modern deep-diving marine mammals, such as whales, the outer shell of the bones is porous. This has the effect of making the bones light enough so that it is easy for the animals to swim back to the surface after a deep dive. The outer shell of the bones was also porous in the ichthyosaur, an extinct prehistoric marine reptile. We can conclude from this that ichthyosaurs were deep divers.

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

Near many cities, contamination of lakes and rivers from pollutants in rainwater runoff exceeds that from industrial discharge. As the runoff washes over buildings and pavements, it picks up oil and other pollutants. Thus, water itself is among the biggest water polluters.

The statement that contamination of lakes and rivers from pollutants in rainwater runoff exceeds that from industrial discharge plays which one of the following roles in the argument?

Theater managers will not rent a film if they do not believe it will generate enough total revenue— including food-and-beverage concession revenue—to yield a profit. Therefore, since film producers want their films to be shown as widely as possible, they tend to make films that theater managers consider attractive to younger audiences.

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

Many nursing homes have prohibitions against having pets, and these should be lifted. The presence of an animal companion can yield health benefits by reducing a person’s stress. A pet can also make one’s time at a home more rewarding, which will be important to more people as the average lifespan of our population increases.

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

Dietary researcher: A recent study reports that laboratory animals that were fed reduced-calorie diets lived longer than laboratory animals whose caloric intake was not reduced. In response, some doctors are advocating reduced-calorie diets, in the belief that North Americans’ life spans can thereby be extended. However, this conclusion is not supported. Laboratory animals tend to eat much more than animals in their natural habitats, which leads to their having a shorter life expectancy. Restricting their diets merely brings their caloric intake back to natural, optimal levels and reinstates their normal life spans.

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

In one study of a particular plant species, 70 percent of the plants studied were reported as having patterned stems. In a second study, which covered approximately the same geographical area, only 40 percent of the plants of that species were reported as having patterned stems.

Which one of the following, if true, most helps to resolve the apparent discrepancy described above?

Scientists have shown that older bees, which usually forage outside the hive for food, tend to have larger brains than do younger bees, which usually do not forage but instead remain in the hive to tend to newly hatched bees. Since foraging requires greater cognitive ability than does tending to newly hatched bees, it appears that foraging leads to the increased brain size of older bees.

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

Most universities today offer students a more in-depth and cosmopolitan education than ever before. Until recently, for example, most university history courses required only the reading of textbooks that hardly mentioned the history of Africa or Asia after the ancient periods, or the history of the Americas’ indigenous cultures. The history courses at most universities no longer display such limitations.

Which one of the following, if true, most strengthens the argument above?

The total number of book titles published annually in North America has approximately quadrupled since television first became available. Retail sales of new titles, as measured in copies, increased rapidly in the early days of television, though the rate of increase has slowed in recent years. Library circulation has been flat or declining in recent years.

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

Many economists claim that financial rewards provide the strongest incentive for people to choose one job over another. But in many surveys, most people do not name high salary as the most desirable feature of a job. This shows that these economists overestimate the degree to which people are motivated by money in their job choices.

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