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?

Ozone in the stratosphere blocks deadly ultraviolet rays from the sun, but chlorofluorocarbons (CFCs) in aerosols and other products have thinned this protective layer. Evidence of this is the ozone hole that forms over the South Pole every Antarctic spring as temperatures drop below – 78 ° C, the temperature at which ozone depletion occurs. Measurements of the ozone hole taken at various times this spring show that, compared with the same times the previous year, its area diminished by four million square kilometers. Nevertheless, scientists have not concluded that the ozone layer is recovering.

Which of the following would, if true, provide the strongest reason for the scientists’ reaction to the measurements?

Biologist: Species with broad geographic ranges probably tend to endure longer than species with narrow ranges. The broader a species’ range, the more likely that species is to survive the extinction of populations in a few areas. Therefore, it is likely that the proportion of species with broad ranges tends to gradually increase with time.

The biologist ’s conclusion follows logically from the above if which of the following is assumed?

Mashika: We already know from polling data that some segments of the electorate provide significant support to Ms. Puerta. If those segments also provide significant support to Mr. Quintana, then no segment of the electorate that provides significant support to Mr. Quintana provides significant support to Mr. Ramirez.

Salim: But actually, as the latest polling data conclusively shows, at least one segment of the electorate does provide significant support to both Mr. Quintana and Mr. Ramirez.

Among the following statements, which is it most reasonable to infer from the assertions by Mashika and Salim?

The recycling of municipal solid waste is widely seen as an environmentally preferable alternative to the prevailing practices of incineration and of dumping in landfills. Recycling is profitable, as the recycling programs already in operation demonstrate. A state legislator proposes that communities should therefore be required to adopt recycling and to reach the target of recycling 50 percent of all solid waste within 5 years.

Which of the following, if true, most seriously calls into question the advisability of implementing the proposal?

Clearbell Telephone provides slow-dialing (SD) service to customers for a low fee, and fast-dialing (FD) service to other customers who pay a somewhat higher fee. FD technology, however, is so efficient that it costs Clearbell substantially less per average call to provide than does SD. Nonetheless, accountants have calculated that Clearbell’s profits would drop if it provided FD to all its customers at the current low-fee rate.

Assume that installation costs for FD are insignificant if the customer already has SD service. Which of the following, if true about Clearbell, best explains the results of the accountants’ calculation?

Beets and carrots are higher in sugar than many other vegetables. They are also high on the glycemic index, a scale that measures the rate at which a food increases blood sugar levels. But while nutritionists usually advise people to avoid high-sugar and high-glycemic-index foods, despite any nutritional benefits they may confer, they are not very concerned about the consumption of beets and carrots.

Which of the following, if true, would best explain the nutritionists’ lack of concern?

Kayla: Many people are reluctant to shop in our neighborhood because street parking is scarce. The city plans to address this by adding parking meters with time limits that ensure that parking spaces are generally available. But this plan will surely backfire—shoppers dislike paying at parking meters, so most will probably drive to other neighborhoods to shop at malls with free parking.

Which of the following, if true, would be the most logically effective rebuttal a proponent of the city’s plan could make to Kayla’s objection?

There are fundamentally two possible changes in an economy that will each cause inflation unless other compensating changes also occur. These changes are either reductions in the supply of goods and services or increases in demand. In a pre-banking economy the quantity of money available, and hence the level of demand, is equivalent to the quantity of gold available.

If the statements above are true, then it is also true that in a pre-banking economy