The need for solar electricity is clear. It is safe, ecologically sound, efficient, continuously available, and it has no moving parts. The basic problem with the use of solar photovoltaic devices is economics, but until recently very little progress had been made toward the development of low-cost photovoltaic devices. The larger part of research funds has been devoted to the study of single-crystal silicon solar cells, despite the evidence that this technique holds little promise. The reason for this pattern is understandable and historical. Crystalline silicon, however, is particularly unsuitable to terrestrial solar cells.
Crystalline silicon solar cells work well and are successfully used in the space program, where cost is not an issue. While single crystal silicon has been proven in extraterrestrial use with efficiencies as high as 18 percent, and other more expensive and scarce materials can have ever higher efficiencies, costs must be reduced by a factor of more that 100 to make them practical for commercial uses. Beside the fact that the starting crystalline silicon is expensive, 95 percent of it is wasted and does not appear in the final device. Recently, there have been some imaginative attempts to make polycrystalline and ribbon silicon which are lower in cost than high-quality single crystals; but to date the efficiencies of these apparently lower-cost materials have been unacceptably small. Moreover, these materials are cheaper only because of the introduction of disordering in crystalline semiconductors, and disorder degrades the efficiency of crystalline solar cells.
This difficulty can be avoided by preparing completely disordered or amorphous materials. Amorphous materials have disordered atomic structure as compared to crystalline materials: that is, they have only short-range order rather that the long-range periodicity of crystals. The advantages of amorphous solar cells are impressive. Whereas crystalline silicon must be made 200 microns thick to absorb a sufficient amount of sunlight for efficient energy conversion, only 1 micron of the proper amorphous materials is necessary. Crystalline silicon solar cells cost in excess of 100 per square foot, but amorphous films can be created at a cost of about 50 cents per square foot.
Although many scientists were aware of the very low cost of amorphous solar cells, they felt that they could never be manufactured with the efficiencies necessary to contribute significantly to the demand for electric power. This was based on a misconception about the feature which determines efficiency. For example, it is not the conductivity of the material in the dark which is relevant, but only the photoconductivity, that is, the conductivity in the presence of sunlight. Already, solar cells with efficiencies well above 6 percent have been developed using amorphous materials, and further research will doubtless find even less costly amorphous materials with higher efficiencies.

59. The author is primarily concerned with _______.
[A] discussing the importance of solar energy
[B] explaining the functioning of solar cells
[C] presenting a history of research on energy sources
[D] describing a possible solution to the problem of the cost of photovoltaic cells
60.The author mentions recent attempts to make polycrystalline and ribbon silicon primarily in order to ______.
[A] minimize the importance of recent improvements in silicon solar cells
[B] demonstrate the superiority of amorphous materials over crystalline silicon
[C] explain why silicon solar cells have been the center of research
[D] contrast crystalline silicon with polycrystalline and ribbon silicon
61. The material in the passage could best be used in an argument for _______.
[A] discontinuing the space program
[B] increased funding for research on amorphous materials
[C] further study of the history of silicon crystals
[D] increased reliance on solar energy
62.The tone of the passage can best be described as _______.
[A] analytical and optimistic
[B] biased and unprofessional
[C] critical and discouraged
[D] hesitating and inconclusive

Passage 4

Although bacteria are unicellular and among the simplest autonomous forms of life, they show a remarkable ability to sense their environment. They are attracted to materials they need and are repelled by harmful substances. Most types of bacteria swim very irregularly; short, smooth runs in relatively straight lines are followed by brief turns, after which the bacteria shoot off in random directions. This leaves researchers with the question of how such bacteria find their way to an attractant such as food or, in the case of photosynthetic bacteria, light, if their swimming pattern consists only of smooth runs and turns, the latter resulting in random changes in direction.
One clue comes from the observation that when a chemical attractant is added to a suspension of such bacteria, the bacteria swim along a gradient of the attractant, from an area where the concentration of the attractant is weaker to an area where it is stronger. As they do so, their swimming is characterized by a decrease in turning and an increase in straight runs over relatively longer distances. As the bacteria encounter increasing concentrations of the attractant, their tendency to turn is suppressed, whereas turning increases whenever they move away from the attractant. The net effect is that runs in the direction of higher concentrations of the attractant become longer and straighter as a result of the suppression of turning, whereas runs away form it are shortened by an increased tendency of the bacteria to change direction.
Biologists have proposed two mechanisms that bacteria might use in detecting changes in the concentration of a chemical attractant. First, a bacterium might compare the concentration of a chemical at the front and back of its cell body simultaneously. If the concentration is higher at the front of the cell, then it knows it is moving up the concentration gradient, from an area where the concentration is lower to an area where it is higher. Alternatively, it might measure the concentration at one instant and again after a brief interval, in which case the bacterium must retain a memory of the initial concentration. Researchers reasoned that if bacteria do compare concentrations at different times, then when suddenly exposed to a uniformly high concentration of an attractant, the cells would behave as if they were swimming up a concentration gradient, with long, smooth runs and relatively few turns. If, on the other hand, bacteria detect a chemical gradient by measuring it simultaneously at two distinct points, front and back, on the cell body, they would not respond to the jump in concentration because the concentration of the attractant in front and back of the cells, though high, would be uniform. Experimental evidence suggests that bacteria compare concentrations at different times.

63. Bacteria detect changes in the concentration of an attractant by _______.
[A] measuring its concentration in front and back of the cell body simultaneously
[B] increasing their motion away from an attractant
[C] moving and tumbling randomly in straight lines
[D] making the concentration of an attractant uniform
64. It can be inferred from the passage that when describing bacteria as "swimming up a concentration gradient" (Para. 3), the author means that they were behaving as if they were swimming _______.
[A] against a resistant medium that makes their swimming less efficient
[B] away from a substance to which they are normally attracted
[C] away from a substance that is normally harmful to them
[D] away from an area where the concentration of a substance is weaker
65. The passage indicates that the pattern that characterizes a bacterium's motion changes in response to _______.
[A] the kinds of chemical attractants present in different concentration gradients
[B] the mechanism that the bacterium adopts in determining the presence of an attractant
[C] the bacterium's detection of changes in the concentration of an attractant
[D] the extent to which neighboring bacteria are engaged in random turning
66. Which of the following statements does the passage support?
[A] The motion of a microorganism can reflect a mechanism by which it is able to control its movement.
[B] Biologists often overstate the complexity of simple organisms such as bacteria.
[C] A bacterium cannot normally retain a memory of a measurement of the concentration of an attractant.
[D] Bacteria appear to have less control over their movement than biologists had previously assumed

Passage 5

The extent of a nation’s power over its coastal ecosystems and the natural resources in its coastal waters has been defined by two international law doctrines: freedom of the seas and adjacent state sovereignty. Until the mid-twentieth century, most nations favored application of broad open-seas freedoms and limited sovereign rights over coastal waters. A nation had the right to include within its territorial dominion only a very narrow band of coastal waters (generally extending three miles from the shoreline), within which it had the authority, but not the responsibility, to regulate all activities. But, because this area of territorial dominion was so limited, most nations did not establish rules for management or protection of their territorial waters.
Regardless of whether or not nations enforced regulations in their territorial waters, large ocean areas remained free of controls or restrictions. The citizens of all nations had the right to use these unrestricted ocean areas for any innocent purpose, including navigation and fishing. Except for controls over its own citizens, no nation had the responsibility, let alone the unilateral authority, to control such activities in international waters. And, since there were few standards of conduct that applied on the “open seas,” there were few jurisdictional conflicts between nations.
The lack of standards is traceable to popular perceptions held before the middle of this century. By and large, marine pollution was not perceived as a significant problem, in part because the adverse effect of coastal activities on ocean ecosystems was not widely recognized, and pollution caused by human activities was generally believed to be limited to that caused by navigation. Moreover, the freedom to fish, or overfish, was an essential element of the traditional legal doctrine of freedom of the seas that no maritime country wished to see limited. And finally, the technology that later allowed exploitation of other ocean resources, such as oil, did not yet exist.
To date, controlling pollution and regulating ocean resources have still not been comprehensively addressed by law, but two recent developments may actually lead to future international rules providing for ecosystem management. First, the establishment of extensive fishery zones, extending territorial authority as far as 200 miles out from a country’s coast, has provided the opportunity for nations individually to manage larger ecosystems. This opportunity, combined with national self-interest in maintaining fish populations, could lead nations to reevaluate policies for management of their fisheries and to address the problem of pollution in territorial waters. Second, the international community is beginning to understand the importance of preserving the resources and ecology of international waters and to show signs of accepting responsibility for doing so. As an international consensus regarding the need for comprehensive management of ocean resources develops, it will become more likely that international standards and policies for broader regulation of human activities that affect ocean ecosystems will be adopted and implemented.

67. According to the passage, until the mid-twentieth century there were few jurisdictional disputes over international waters because _______.
[A] the nearest coastal nation regulated activities
[B] few controls or restrictions applied to ocean areas
[C] the ocean areas were used for only innocent purposes
[D] broad authority over international waters was shared equally among all nations
68.The author suggests that, before the mid-twentieth century, most nations’ actions with respect
to territorial and international waters indicated that ______.
[A] managing ecosystems in either territorial or international waters was given low priority
[B] unlimited resources in international waters resulted in little interest in territorial waters
[C] nations considered it their responsibility to protect territorial but not international waters
[D] a nation’s authority over its citizenry ended at territorial lines
69.Which one of the following does the author cite as an effect of the extension of territorial
waters beyond the three-mile limit?
[A] increased political pressure on individual nations to establish comprehensive laws regulation ocean resources
[B] a greater number of jurisdictional disputes among nations over the regulation of fishing on the open seas
[C] the opportunity for some nations to manage large ocean ecosystems
[D] a new awareness of the need to minimize pollution caused by navigation
70. The passage as a whole can best be described as _______.
[A] a legal inquiry into the abuse of existing laws and the likelihood of reform
[B] a political analysis of the problems inherent in directing national attention to an international issue
[C] a historical analysis of a problem that requires international attention
[D] a proposal for adopting and implementing international standards to solve an ecological problem

Section IV English-Chinese Translation

Directions:
Read the following passage carefully and then translate the underlined sentences into Chinese. Your translation must be written neatly on ANSWER SHEET 2.

71) Economic growth involves increases over time in the volume of a country's per capita gross national product (GNP) of goods and services. Such continuing increases can raise average living standards substantially and provide a stronger base for other policy objectives. 72) It is only in the last two centuries that continued growth in living standards has been realized for a number of now-developed countries, and this process has broadened in the 20th century to include a number of developing countries. 73) However, the fairly steady expansion in the third quarter of the 20th century gave way to a period of slower and more erratic growth for both high- and low-income countries, while some of the economically poorest countries were thus far unable to establish a self-sustaining pattern of development. It also became increasingly evident that there were serious environmental problems associated with some types of growth in production.
In examining the record of economic growth and development, economists offer some explanations for the changes involved, and the attempts by governments to plan these changes. Five major issues are involved. The first is why economic growth occurs more quickly in some countries and periods than in others. It is the increase in the size and quality of the factors of production that underlies growth, but certain forces deserve special attention. A variety of models of economic growth give expression to the understanding of these forces. Increasing attention has been paid in these models and in policy to the international aspects of growth. This trend is partly a reflection of the growing internationalization of economic activity. It also reflects a number of potentially destabilizing changes in the international economy that became evident during the 1970s.
74) A second issue is the challenges facing the low-income countries, namely, to move from subsistence levels of per capita income to a level that would generate self-sustaining growth and also to reduce the gap between themselves and the higher-income countries. A third issue, productivity, is central to changes in living standards and to the analysis of international competitiveness.
A fourth major issue is the attempt to maintain growth and increase development through economic planning. 75) Planning became a widespread phenomenon during and just after World War II and was given further emphasis in many newly independent countries that were industrializing. Beginning in the 1970s the emphasis shifted to more decentralized planning, with deregulation and privatization of industry as two aspects of this process.
Underlying economic growth and planning is a fifth issue, the attempt to predict economic activity. Modern forecasting involves a variety of computer-based techniques at the level of the firm, the country, and the international economy. The accuracy of forecasting has been reduced by increased uncertainty in the global and national economies since the early 1970s.

Section V Writing

Directions:
E. Title: The Significance of Population Census to Our Country
F. Write an essay of at least 200 words
G. Your composition should be based on the OUTLINE below
H. Your composition should be written neatly on ANSWER SHEET 2.

Outline:
a. The importance of population census to our country
b. The difficulties in counting the population
c. Suggested ways of overcoming the difficulties

模拟试题二答案
Section I Structure and vocabulary
1. A 2.A 3.B 4.B 5. A 6.C 7.B 8.B 9.A 10.A
11. B 12.A 13.C 14.D 15.D 16.B 17.D 18.B 19.D 20.B
21.B 22.B 23.A 24.B 25.A 26.C 27.B 28.C 29.A 30.C

Section II Cloze
31. B 32.C 33.D 34.A 35.B 36.A 37.B 38.A 39.C 40.D
41. C 42.A 43.C 44.B 45.D 46.A 47.B 48.C 49.A 50.D

Section III Reading Comprehension
51. A 52. B 53. A 54. D 55. B 56. D 57. C 58. C 59. D 60. A
61. B 62. A 63. B 64. D 65. C 66. A 67. B 68. A 69. C 70. C

Section IV English-Chinese Translation
71. 经济增长指在一定时间内一个国家的包括产品和服务在内的人均国民生产总值在量上 的增加。
72．只是在过去的200年里，现在成为发达国家的几个国家才实现了生活标准的持续提高，在二十世纪，这一（提高）过程扩大到几个发展中国家。
73．然而，二十世纪六、七十年代相当稳定的提高过程，无论是在高收入国家还是在低收入国家都被一个缓慢而不稳定的提高阶段所取代，而某些经济最落后的国家根本无法建立起一种持续发展的模式。
74．第二个问题涉及到低收入国家所面临的挑战，即：从人均收入只足以维持生计水平提高到一个能产生持续发展的水平，并同时缩小自己与高收入国家的差距。
75．第二次世界大战期间和刚刚结束以后，计划成为一种普遍现象，许多刚取得独立并正在实行工业化的国家更是强调计划的重要性。

Section V Writing （略）

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