Critic to economist: In yet another of your bumbling forecasts, last year you predicted that this country’s economy would soon go into recession if current economic policies were not changed. Instead, economic growth is even stronger this year.

Economist: There was nothing at all bumbling about my warning. Indeed, it convinced the country’s leaders to change economic policies, which is what prevented a recession.

The economist responds to the critic by

Hospitals, universities, labor unions, and other institutions may well have public purposes and be quite successful at achieving them even though each of their individual staff members does what he or she does only for selfish reasons.

Which one of the following generalizations is most clearly illustrated by the passage?

Consumer advocate: In some countries, certain produce is routinely irradiated with gamma rays in order to extend shelf life. There are, however, good reasons to avoid irradiated foods. First, they are exposed to the radioactive substances that produce the gamma rays. Second, irradiation can reduce the vitamin content of fresh foods, leaving behind harmful chemical residues. Third, irradiation spawns unique radiolytic products that cause serious health problems, including cancer.

Each of the following, if true, weakens the consumer advocate’s argument EXCEPT:

When teaching art students about the use of color, teachers should use colored paper rather than paint in their demonstrations. Colored paper is preferable because it readily permits a repeated use of exactly the same color in different compositions, which allows for a precise comparison of that color’s impact in varying contexts. With paint, however, it is difficult to mix exactly the same color twice, and the varying textures of the applied paint can interfere with the pure effect of the color itself.

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

Philosopher: To explain the causes of cultural phenomena, a social scientist needs data about several societies: one cannot be sure, for example, that a given political structure is brought about only by certain ecological or climatic factors unless one knows that there are no similarly structured societies not subject to those factors, and no societies that, though subject to those factors, are not so structured.

The claim that to explain the causes of cultural phenomena, a social scientist needs data about several societies plays which one of the following roles in the philosopher’s reasoning?