According to the passage, the more protein a rat consumes, the lower will be theA．ratio of

A．they would eventually need to design experiments that involved feeding rats high concentrations of protein.

B．tryptophan levels in the blood were difficult to monitor with accuracy.

C．serotonin levels increased after rats were fed meals rich in tryptophan.

D．there were many neurotransmitters whose production was dependent on metabolic processes elsewhere in the body.

E．serotonin levels increased after rats were injected with a large amount of tryptophan.

According to the passage, the floor of the Black Sea can best be compared to a

A．rapidly moving conveyor belt.

B．slowly settling foundation.

C．rapidly expanding balloon.

D．violently erupting volcano.

E．slowly eroding mountain.

on both sides?

A．The Pacific Ocean and the Sea of Japan.

B．The South Atlantic Ridge and the North Sea Ridge.

C．The Gulf of Mexico and the South Atlantic Ridge.

D．The Mid-Atlantic Ridge and the Indian Ocean Ridge.

E．The Black Sea and the Sea of Japan.

The author refers to a "conveyor belt " in line 16 in order to

A．illustrate the effects of convection in the mantle.

B．show how temperature differences depend on the positions of the continents.

C．demonstrate the linear nature of the Mid-Atlantic Ridge.

D．describe the complicated motions made possible by back-coupling.

E．account for the rising currents under certain mid-ocean ridges.

s, corporate response to federal requirements(lines 23 — 24)was substantial?

A．Corporate contracts with minority-owned businesses totaled $ 2 billion in 1979.

B．Between 1970 and 1972, corporate contracts with minority-owned businesses declined by 25 percent.

C．The figures collected in 1977 under-represented the extent of corporate contracts with minority-owned businesses.

D．The estimate of corporate spending with minority-owned businesses in 1980 is approximately $ 10 million too high.

E．The $1.1 billion represented the same percentage of total corporate spending in 1977 as did $ 77 million in 1972.

tions are often temporary and, over long periods, trivial. Scientists have advanced three theories of population control to account for this relative constancy. The first theory attributes a relatively constant population to periodic cli- matic catastrophes that decimate populations with such frequency as to prevent them from exceeding some particular limit. In the case of small organisms with short life cycles, climatic changes need not be catastrophic: normal seasonal changes in photoperiod(daily amount of sunlight), for example, can govern population growth. This theory— the density-independent view—asserts that climatic factors exert the same regulatory effect on population regardless of the number of individuals in a region. A second theory argues that population growth is primarily density-de- pendent—that is, the rate of growth of a population in a region decreases as the number of animals increases. The mechanisms that manage regulation may vary. For example, as numbers in- crease, the food supply would probably diminish, which would increase mortality. In addition, as Lotka and Volterra have shown, predators can find prey more easily in high-density populations. Other regulators include physiological control mechanisms: for example, Christian and Davis have demonstrated how the crowding that results from a rise in numbers may bring about hor- monal changes in the pituitary and adrenal glands that in turn may regulate population by lowering sexual activity and inhibiting sexual maturation. There is evidence that these effects may persist for three generations in the absence of the original provocation. One challenge for density-dependent theorists is to develop models that would allow the precise prediction of the effects of crowding. A third theory, proposed by Wynne- Edwards and termed "epideic-tic," argues that organisms have evolved a "code"in the form. of social or epideic- tic behavior. displays, such as winterroosting aggregations or group vocalizing; such codes provide organisms with information on population size in a region so that they can, if necessary, ex- ercise reproductive restraint. However, Wynne-Edwards theory, linking animal social behavior. and population control, has been challenged, with some justification, by several studies.

The primary purpose of the passage is to

A．argue against those scientists who maintain that animal populations tend to fluctuate.

B．compare and contrast the density-dependent and epideictic theories of population control.

C．provide example of some of the ways in which animals exercise reproductive restraint to control their own numbers.

D．suggests that theories of population control that concentrate on the social behavior. of animals are more open to debate than are theories that do not.

E．summarize a number of scientific theories that attempt to explain why animal populations do not exceed certain limits.

I, " insisting that the correct phrasing is "between you and me," with the objective case after a preposition. Such condemnations, however, are obviously unfounded, because Shakespeare himself, in The Merchant of Venice, wrote, "All debts are cleared between you and I. " Which of the following, if true, most seriously weakens the argument above?

A．In his plays, Shakespeare intentionally had some of his characters use phrases he considered ungrammatical.

B．The phrase "between you and I" appears infrequently in Shakespeare"s writings.

C．The more modern an English word or phrase, the less likely that modern grammarians will consider it acceptable for formal usage.

D．Many modern speakers of English sometimes say "between you and I" and sometimes say "between you and me. "

E．Most native speakers of English who choose to say "between you and I" do so because they know that Shakespeare used that phrase.

lop the Earth as a result of nuclear war. Atmospheric scientists and weather experts cannot reliably and accurately predict tomorrow s weather. Yet the effect of nuclear explosions on local and worldwide atmospheric conditions must follow the same laws that control everyday weather changes. If the weather cannot be predicted with present knowledge, neither can a nuclear-winter scenario. Which of the following, if true, would most seriously weaken the argument made above that if scientists cannot reliably predict the daily weather, their predictions of a " nuclear winter" cannot be believed?

A．The scientific theory of a nuclear winter uses data that is available to those who forecast the daily weather.

B．Scientists" predictions about a nuclear winter are necessarily speculative, since they cannot be verified by harmless experimentation.

C．Weather forecasters usually do not insist that their predictions are infallible.

D．Scientific predictions of catastrophic natural events such as volcanic eruptions and earthquakes usually have less reliability than everyday weather predictions.

E．The scientific theory of a nuclear winter is concerned with drastic climatic changes rather than day-to-day fluctuations in the weather.

ted around 1820, but some sixteenth-century European maps show a body that resembles the polar landmass, even though explorers of the period never saw it. Some scholars, therefore, argue that the continent must have been discovered and mapped by the ancients, whose maps are known to have served as models for the European cartographers. Which of the following, if true, is most damaging to the inference drawn by the scholars?

A．The question of who first sighted Antarctica in modern times is still much debated, and no one has been able to present conclusive evidence.

B．Between 3,000 and 9,000 years ago, the world was warmer than it is now, and the polar landmass was presumably smaller.

C．There are only a few sixteenth-century global maps that show a continental landmass at the South Pole.

D．Most attributions of surprising accomplishments to ancient civilizations or even extraterrestrials are eventually discredited or rejected as preposterous.

E．Ancient philosophers believed that there had to be a large landmass at the South Pole to balance the northern continents and make the world symmetrical.

from accidents and unsafe conditions on the job. There has actually been an increase in the number of job-related accidents under OSHA. This demonstrates the agencys ineffectiveness. Which of the following, if true, concerning the period during which the increase occurred, most seriously weakens the argument above?

A．A number of job categories, excluded from the jurisdiction of OSHA in the legislation originally establishing the agency, have continued to be outside OSHA"s jurisdiction.

B．OSHA has been assigned a greater number of kinds of workplace activities to monitor.

C．There has been an increase in the total number of people at work, and the ratio of work-related deaths and injuries to size of work force has fallen in OSHA-supervised occupations.

D．Regulations issued by OSHA have met with political criticism from elected officials and the mass media.

E．The increase in job-related accidents has occurred mainly in a single job category, whereas the number of job-related accidents has remained approximately constant in other categories.