gre考试阅读真题解析(B)

　　It is their sensitive response to human circumstance that accounts for the persistence of certain universal ideas. Rabbi Meir, a second-century scholar, admonished his disciples to look not at the pitcher but at its contents because, he stated, Many a new pitcher has been found to be full of old wine. This was his way of emphasizing the importance of the distinction between form and idea, and of stressing that the integrity of an idea is more important than the form of its expression.

　　Creative ideas not only produce their own instruments of survival as time and circumstances demand, but permit the substitution of new forms for old under the pressure of changed circumstances. For example democracy, as an idea, originated in ancient Greece and was carried from there to Western Europe and the Americas. But it did not retain the ancient Greek form: it passed through several reforming processes and exists today in many countries. Democratic governments differ in form because democracy is in principle dynamic and has therefore responded to local needs.

　　17. The author is primarily concerned with

　　 illustrating the importance of a historical figure

　　 discussing an important characteristic of human ideas

　　 describing the history of the growth of democracy

　　 contrasting ancient and modern views of the importance of creative ideas

　　 evaluating the contribution of ancient Greece to modern government

　　18. According to the passage, democracy is an example of

　　 a human circumstance that has molded creative ideas

　　 an instrument of survival that has altered its original form

　　 an attribute of a creative idea that has allowed that idea to persist

　　 a creative idea that has persisted because of its adaptability

　　 a reforming process that has culminated in the creation of modern governments

　　19. The new pitcher mentioned in line 6 is the equivalent of which of the following elements in the authors discussion of democracy ?

　　 Ancient Greece

　　 The idea of democracy

　　 A modern democratic government

　　 A dynamic principle

　　 The Greek form of democracy

　　20. It can be inferred from the passage that the author would disagree most with which of the following assertions?

　　 Changing circumstances sometimes give rise to original ideas.

　　 Creative ideas have universal applications.

　　 Changing human needs influence universal ideas.

　　 Democratic institutions are appropriate in the modern world.

　　 An idea must be expressed in a traditional way.

　　Before 1965 many scientists pictured the circulation of the oceans water mass as consisting of large, slow-moving currents, such as the Gulf Stream . That view, based on 100 years of observations made around the globe, produced only a rough approximation of the true circulation. But in the 1950s and the 1960s, researchers began to employ newly developed techniques and equipment, including subsurface floats that move with ocean currents and emit identification signals, and ocean-current meters that record data for months at fixed locations in the ocean. These instruments disclosed an unexpected level of variability in the deep ocean. Rather than being characterized by smooth, large-scale currents that change seasonally , the seas are dominated by what oceanographers call mesoscale fields: fluctuating, energetic flows whose velocity can reach ten times the mean velocity of the major currents.

　　Mesoscale phenomenathe oceanic analogue of weather systemsoften extend to distances of 100 kilometers and persist for 100 days . More than 90 percent of the kinetic energy of the entire ocean may be accounted for by mesoscale variability rather than by large-scale currents. Mesoscale phenomena may, in fact, play a significant role in oceanic mixing, air-sea interactions, and occasionalbut far-reachingclimatic events such as El Nino, the atmospheric-oceanic disturbance in the equatorial Pacific that affects global weather patterns.

　　Unfortunately, it is not feasible to use conventional techniques to measure mesoscale fields. To measure them properly, monitoring equipment would have to be laid out on a grid at intervals of at most 50 kilometers, with sensors at each grid point lowered deep in the ocean and kept there for many months. Because using these techniques would be prohibitively expensive and time-consuming, it was proposed in 1979 that tomography be adapted to measuring the physical properties of the ocean. In medical tomography x-rays map the human bodys density variations ; the information from the x-rays, transmitted through the body along many different paths, is recombined to form three-dimensional images of the bodys interior. It is primarily this multiplicative increase in data obtained from the multipath transmission of signals that accounts for oceanographers attraction to tomography: it allows the measurement of vast areas with relatively few instruments. Researchers reasoned that low-frequency sound waves, because they are so well described mathematically and because even small perturbations in emitted sound waves can be detected, could be transmitted through the ocean over many different paths and that the properties of the oceans interiorits temperature, salinity, density, and speed of currentscould be deduced on the basis of how the ocean altered the signals. Their initial trials were highly successful, and ocean acoustic tomography was born.

　　21. According to the passage, scientists are able to use ocean acoustic tomography to deduce the properties of the oceans interior in part because

　　 low-frequency sound waves are well described mathematically

　　 mesoscale phenomena are so large as to be easily detectable

　　 information from sound waves can be recombined more easily than information from x-rays

　　 tomography is better suited to measuring mesoscale phenomena than to measuring small-scale systems

　　 density variations in the ocean are mathematically predictable

　　22. The passage suggests that medical tomography operates on the principle that

　　 x-rays are superior to sound waves for producing three-dimensional images

　　 sound waves are altered as they pass through regions of varying density

　　 images of the bodys interior can be produced by analyzing a single x-ray transmission through the body

　　 the varying densities within the human body allow x-rays to map the internal organs

　　 information from x-rays and sound waves can be combined to produce a highly detailed image of the bodys interior

　　23. Which of the following is most similar to medical tomography as it is described in the passage?

　　 The use of ocean-current meters to determine the direction and velocity of the oceans mesoscale fields

　　 The use of earthquake shockwave data collected at several different locations and combined to create a three-dimensional image of the Earths interior

　　 The use of a grid-point sensory system to map global weather patterns

　　 The use of subsurface floats to map large-scale circulation in the ocean

　　 The use of computer technology to halt the progress of a particular disease within the human bodys internal organs

　　24. The author mentions El Nino primarily in order to emphasize which of the following points?

　　 The brief duration of weather patterns

　　 The variability of mesoscale phenomena

　　 The difficulty of measuring the oceans large-scale currents

　　 The effectiveness of low-frequency sound waves in mapping the ocean

　　 The possible impact of mesoscale fields on weather conditions

　　25. Which of the following best describes the organization of the third paragraph of the passage?

　　 A theory is proposed, considered, and then attended.

　　 Opposing views are presented, elaborated, and then reconciled.

　　 A problem is described, then a solution is discussed and its effectiveness is affirmed.

　　 An argument is advanced, then refuted, and an alternative is suggested.

　　 A hypothesis is presented, qualified, and then reaffirmed.

　　26. The passage suggests that which of the following would be true if the oceans circulation consisted primarily of large, slow-moving currents?

　　 The influence of mesoscale fields on global weather patterns would remain the same.

　　 Large-scale currents would exhibit more variability than is actually observed.

　　 The majority of the oceans kinetic energy would be derived from mesoscale fields.

　　 Atmospheric-oceanic disturbances such as El Nino would occur more often.

　　 Conventional measuring techniques would be a feasible method of studying the physical properties of the ocean.

　　27. Which of the following, if presented as the first sentence of a succeeding paragraph, would most logically continue the discussion presented in the passage?

　　 Timekeeping in medical tomography must be precise because the changes in travel time caused by density fluctuations are slight.

　　 To understand how ocean acoustic tomography works, it is necessary to know how sound travels in the ocean.

　　 Ships are another possibility, but they would need to stop every 50 kilometers to lower measuring instruments.

　　 These variations amount to only about 2 to 3 percent of the average speed of sound in water, which is about 1, 500 meters per second.

　　 The device used in medical tomography emits a specially coded signal, easily distinguishable from background noise.

答案：17-27：BDCEADBECEB