1、大学英语六级模拟试卷 227及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a letter on behalf of the Students Union and the Academic Lectures Association to invite a visiting foreign professor, David, to deliver a presentation to the students in your univers
2、ity. You are NOT allowed to include the name of your university in this letter. You should write at least 150 words following the outline given below. 1. 对这位知名的外籍教授的到来表示欢迎 2表达希望该教授就某个话题在学校进行讲座的希望和对 讲座的一些基本设想 3希望教授可以接受邀请，并对教授的宝贵时间表示感谢 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minut
3、es) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark： Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradicts the information give
4、n in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Greenhouse Effect . Introduction Greenhouse Effect, the capacity of certain gases in the atmosphere to trap heat emitted from the Earths surface, thereby insulating and warming the Earth. Without the thermal blank
5、eting of the natural greenhouse effect, the Earths climate would be about 33 Celsius degrees coolertoo cold for most living organisms to survive. The greenhouse effect has warmed the Earth for over 4 billion years. Now scientists are growing increasingly concerned that human activities may be modify
6、ing this natural process, with potentially dangerous consequences. Since the advent of the Industrial Revolution in the 1700s, humans have devised many inventions that burn fossil fuels such as coal, oil, and natural gas. Burning these fossil fuels, as well as other activities such as clearing land
7、for agriculture or urban settlements, releases some of the same gases that trap heat in the atmosphere, including carbon dioxide, methane, and nitrous oxide. These atmospheric gases have risen to levels higher than at any time in the last 420,000 years. As these gases build up in the atmosphere, the
8、y trap more heat near the Earths surface, causing Earths climate to become warmer than it would naturally. Scientists call this unnatural heating effect global warming and blame it for an increase in the Earths surface temperature of about 0.6 Celsius degrees over the last nearly 100 years. Without
9、remedial measures, many scientists fear that global temperatures will rise 1.4 to 5.8 Celsius degrees by 2100. These warmer temperatures could melt parts of polar ice caps and most mountain glaciers, causing a rise in sea level of up to lm within a century or two, which would flood coastal regions.
10、Global warming could also affect weather patterns causing, among other problems, prolonged drought or increased flooding in some of the worlds leading agricultural regions. . How the Greenhouse Effect Works The greenhouse effect results from the interaction between sunlight and the layer of greenhou
11、se gases in the Earths atmosphere that extends up to 100 km above Earths surface. Sunlight is composed of a range of radiant energies known as the solar spectrum, which includes visible light, infrared light (红外线 ), X-rays, and ultraviolet light. When the Suns radiation reaches the Earths atmosphere
12、, some 25 percent of the energy is reflected back into space by clouds and other atmospheric particles. About 20 percent is absorbed in the atmosphere. For instance, gas molecules in the uppermost layers of the atmosphere absorb the Suns X-rays. The Suns ultraviolet (紫外线的 ) radiation is absorbed by
13、the ozone layer, located 19 to 48 km above the Earths surface. About 50 percent of the Suns energy, largely in the form of visible light, passes through the atmosphere to reach the Earths surface. Soils, plants, and oceans on the Earths surface absorb about 85 percent of this heat energy, while the
14、rest is reflected back into the atmospheremost effectively by reflective surfaces such as snow, ice, and sandy deserts. In addition, some of the Suns radiation that is absorbed by the Earths surface becomes heat energy in the form of long-wave infrared radiation, and this energy is released back int
15、o the atmosphere. Certain gases in the atmosphere, including water vapor, carbon dioxide, methane, and nitrous oxide, absorb this infrared radiant heat, temporarily preventing it from dispersing into space. As these atmospheric gases warm, they in mm emit infrared radiation in all directions. Some o
16、f this heat returns back to Earth to further warm the surface in what is known as the greenhouse effect, and some of this heat is eventually released to space. This heat transfer creates equilibrium between the total mount of heat that reaches the Earth from the Sun and the amount of heat that the E
17、arth radiates out into space. This equilibrium or energy balancethe exchange of energy between the Earths surface, atmosphere, and spaceis important to maintain a climate that can support a wide variety of life. The heat-trapping gases in the atmosphere behave like the glass of a greenhouse. They le
18、t much of the Suns rays in, but keep most of that heat from directly escaping. Because of this, they are called greenhouse gases. Without these gases, heat energy absorbed and reflected from the Earths surface would easily radiate back out to space, leaving the planet with an inhospitable temperatur
19、e close to-19 , instead of the present average surface temperature of 15 . To appreciate the importance of the greenhouse gases in creating a climate that helps sustain most forms of life, compare Earth to Mars and Venus (金星 ). Mars has a thin atmosphere that contains low concentrations of heat-trap
20、ping gases. As a result, Mars has a weak greenhouse effect resulting in a largely frozen surface that shows no evidence of life. In contrast, Venus has an atmosphere containing high concentrations of carbon dioxide. This heat-trapping gas prevents heat radiated from the planets surface from escaping
21、 into space, resulting in surface temperatures that average 462 too hot to support life. . Understanding the Greenhouse Effect Although concern over the effect of increasing greenhouse gases is a relatively recent development, scientists have been investigating the greenhouse effect since the early
22、1800s. French mathematician and physicist Jean Baptist Joseph Fourier, while exploring how heat is conducted through different materials, was the first to compare the atmosphere to a glass vessel in 1827. Fourier recognized that the air around the planet lets in sunlight, much like a glass roof. In
23、the 1850s British physicist John Tyndall investigated the transmission of radiant heat through gases and vapors. Tyndall found that nitrogen and oxygen, the two most common gases in the atmosphere, had no heat-absorbing properties. He then went on to measure the absorption of infrared radiation by c
24、arbon dioxide and water vapor, publishing his findings in 1863 in a paper titled “On Radiation Through the Earths Atmosphere.“ Swedish chemist Svante August Arrhenius, best known for his Nobel Prize-winning work in electrochemistry, also advanced understanding of the greenhouse effect. In 1896 he ca
25、lculated that doubling the natural concentrations of carbon dioxide in the atmosphere would increase global temperatures by 4 to 6 Celsius degrees, a calculation that is not too far from todays estimates using more sophisticated methods. Arrhenius correctly predicted that when Earths temperature war
26、ms, water vapor evaporation from the oceans increases. The higher concentration of water vapor in the atmosphere would then contribute to the greenhouse effect and global warming. Today scientists around the world monitor atmospheric greenhouse gas concentrations and create forecasts about their eff
27、ects on global temperatures. Air samples from sites spread across the globe are analyzed in laboratories to determine levels of individual greenhouse gases. Sources of greenhouse gases, such as automobiles, factories, and power plants, are monitored directly to determine their emissions. Scientists
28、gather information about climate systems and use this information to create and test computer models that simulate how climate could change in response to changing conditions on the Earth and in the atmosphere. These models act as high-tech crystal balls to project what may happen in the future as g
29、reenhouse gas levels rise. Models can only provide approximations, and some of the predictions based on these models often spark controversy within the science community. Nevertheless, the basic concept of global warming is widely accepted by most climate scientists. . Efforts to Control Greenhouse
30、Gases Due to overwhelming scientific evidence and growing political interest, global warming is currently recognized as an important national and international issue. Since 1992 representatives from over 160 countries have met regularly to discuss how to reduce worldwide greenhouse gas emissions. In
31、 1997 representatives met in Kyoto, Japan, and produced an agreement, known as the Ky0to Protocol, which requires industrialized countries to reduce their emissions by 2012 to an average of 5 percent below 1990 levels. To help countries meet this agreement cost-effectively, negotiators are trying to
32、 develop a system in which nations that have no obligations or that have successfully met their reduced emissions obligations could profit by selling or trading their extra emissions quotas to other countries that are struggling to reduce their emissions. Negotiating such detailed emissions trading
33、rules has been a contentious task for the world community since the signing of the Kyoto Protocol. A ratified agreement is still not yet in force, and ratification received a setback in 2001 when newly elected U.S. president George W. Bush renounced the treaty on the grounds that the required carbon
34、-dioxide reductions in the United States would be too costly. He also objected that developing nations would not be bound by similar carbon-dioxide reducing obligations. However, many experts expect that as the scientific evidence about the dangers of global warming continues to mount, nations will
35、be motivated to cooperate more effectively to reduce the risks of climate change. 2 Greenhouse Effect results from insulating and warming the Earth. （ A） Y （ B） N （ C） NG 3 Without the thermal blanketing of the natural greenhouse effect, most living organisms would die. （ A） Y （ B） N （ C） NG 4 The g
36、reenhouse effect has warmed the Earth when the Earth came into being. （ A） Y （ B） N （ C） NG 5 Earths climate would surely become warmer and warmer. （ A） Y （ B） N （ C） NG 6 The solar spectrum includes visible light, infrared light, X-rays, and _. 7 Some of the Suns radiation that is absorbed by the E
37、arths surface becomes heat energy in the form of _. 8 Mars has a thin atmosphere that contains low concentrations of _. 9 British physicist John Tyndall investigated the transmission of radiant heat through _. 10 Scientists gather information about climate systems and use this information to _. 11 G
38、lobal warming is currently recognized as an important _. Section A Directions: In this section, you will hear 8 short conversations and 2 long conversations. At the end of each conversation, one or more questions will be asked about what was said. Both the conversation and the questions will be spok
39、en only once. After each question there will be a pause. During the pause, you must read the four choices marked A, B, C and D, and decide which is the best answer. （ A） At Annes Clothing Store. （ B） Inside a shopping center. （ C） At a downtown street. （ D） In a suburban residential district （ A） He
40、 was fired from his job. （ B） He was warned about being morepunctual from now on. （ C） The management cat his working hours. （ D） He was promoted （ A） They are at a violin shop. （ B） They axe at a circus. （ C） They are at a concert. （ D） They are inside a movie theatre （ A） She didnt go to work this
41、 morning. （ B） She was injured and had to go to the hospital. （ C） She talked with the boss in the morning. （ D） The traffic delayed her （ A） Seven oclock. （ B） Seven thirty. （ C） Eight oclock. （ D） Eight thirty （ A） Sending the next package earlier. （ B） Waiting patiently. （ C） Using air freight. （
42、 D） Looking for the package （ A） She thinks that he should plan his money more carefully. （ B） She thinks that he should buy a convertible. （ C） She thinks that he should ask Barbara for advice. （ D） She wants him to manage her money （ A） He was furious with his boss. （ B） He was always late to work
43、. （ C） His daughter was sick and that made him late for work. （ D） He prepared a financial report incorrectly （ A） On the line. （ B） On the plane. （ C） In the restaurant. （ D） In the police office. （ A） 14 Spring Vale. （ B） 40 Spring Well （ C） 14 Spring Well. （ D） 40 Spring Vale. （ A） Leave the ladd
44、er around. （ B） Cancel the milk. （ C） Not to tell others including the neighbors shes away. （ D） Not to cancel the paper. （ A） Because they are sister and brother. （ B） Because they lost connections for a long time and he wants to keep in touch with her. （ C） Because they are best friends. （ D） Beca
45、use Mike wants some advice from Sue for job interview. （ A） She was sick. （ B） She lost her job. （ C） She said goodbye to her boyfriend. （ D） She failed in the interview. （ A） How long I intend to stay in the job? （ B） How much Im paid in my present job? （ C） How much I expect to be paid in the new
46、job? （ D） What is your interest or hobby? （ A） 1. （ B） 2. （ C） 3. （ D） 4. Section B Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must
47、choose the best answer from the four choices marked A, B, C and D. （ A） They will find out what its people like. （ B） They will argue in favor of this country and the language. （ C） They will know the country and its people better. （ D） They will like its inhabitants and their language. （ A） It is f
48、rom second-hand information. （ B） It is from the arguments about the country. （ C） It is different from what one had before the travel. （ D） It is gathered from other sources than from its inhabitants. （ A） Differences between people will gradually disappear. （ B） Differences between people will not
49、 exist as one hopes. （ C） Differences between people will always continue to exist and the world will be a dull place. （ D） Differences between people do exist even though different nationalities behave exactly alike. （ A） In the blue pages. （ B） In the white pages. （ C） In the yellow pages. （ D） In a special section. （ A） Right after the white pages. （ B） In the front of the white pages. （ C） At the end of the telephone book. （ D） On the first page of the teleph
