A.A prototype fuel-efficient vehicle, built five years ago, achieves a very high 81 miles per gallon on the highway and 63 in the city, but its materials are relatively costly.
B.Small cars sold by manufacturers in the United States are more fuel efficient now than before the sudden jump in oil prices in 1973.
C.Automakers elsewhere in the world have slowed the introduction of fuel-efficient technologies but have pressed ahead with research and development of them in preparation for a predicted rise in world oil prices.
D.There are many technological opportunities for reducing the waste of energy in cars and light trucks through weight, aerodynamic drag, and braking friction.
E.The promotion of mass transit over automobiles as an alternative mode of transportation has encountered consumer resistance that is due in part to the failure of mass transit to accommodate the wide dispersal of points of origin and destinations for trips.
第1题
According to the passage, Fabian s theory makes use of which of the following principles?
A.Gas emanating from an explosion will be hotter the more distant it is from the origin.
B.The wavelength of radiation emitted by a gas as it cools remains constant.
C.If pressure remains constant, the volume of a gas will decrease as it is cooled.
D.The volume of a gas will increase as the pressure increases.
E.As gas cools, its density decreases.
第2题
The author of the passage probably mentions Canizares determination in order to
A.clarify an ambiguity in Fabian"s research findings.
B.illustrate a generalization about the temperature of gas in a galaxy cluster.
C.introduce a new argument in support of the orthodox view of galaxies.
D.provide support for Fabian"s assertions about the Perseus galaxies.
E.provide an alternate point of view concerning the movement of gas within a galaxy cluster.
第3题
Which of the following best describes the organization of the passage?
A.A problem is described, and then reasons why various proposed solutions succeeded or failed are discussed.
B.A problem is described, and then an advantage of resolving it is offered.
C.A problem is described, and then reasons for its continuing existence are summarized.
D.The historical origins of a problem are described, and then various measures that have successfully resolved it are discussed.
E.The causes of a problem are described, and then its effects are discussed.
第4题
According to the passage, the more protein a rat consumes, the lower will be the
A.ratio of the rat" s blood-tryptophan concentration to the amount of serotonin produced and released in the rat"s brain.
B.ratio of the rat"s blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein.
C.ratio of the rat"s blood-tyrosine concentration to its blood-leucine concentration.
D.number of neurotransmitters of any kind that the rat will produce and release.
E.number of amino acids the rat" s blood will contain.
第5题
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.
第6题
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.
第7题
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.
第8题
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.
第9题
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.
第10题
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.
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