[外语类试卷]大学英语六级模拟试卷249及答案与解析.doc

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1、大学英语六级模拟试卷 249及答案与解析 一、 Part I Writing (30 minutes) 1 Direction: For this part you are allowed 30 minutes to write a composition on the topic On Stress. You should write no less than 150 words and base your composition on the online below. 1. 有的人害怕 压力。 2有的人认为压力并不是一件坏事。 3我的看法。 二、 Part II Reading Comp

2、rehension (Skimming and Scanning) (15 minutes) 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

3、 statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Factors Threatening the Environment The problems facing the environment are vast and diverse. Global warming, the depletion of the ozone layer in the atmosphere, and dest

4、ruction of the worlds rain forests are just some of the Problems that many scientists believe will reach critical proportions in the coming decades. All of these problems will be directly affected by the size of the human population. A. Population Growth Human population growth is at the root of vir

5、tually all of the worlds environmental problems. Although the growth rate of the worlds population has slowed slightly since the 1990s, the worlds population increases by about 77 million human beings each year. As the number of people increases, crowding generates pollution, destroys more habitats,

6、 and uses up additional natural resources. The Population Division of the United Nations (UN) predicts that the worlds population will increase from 6.23 billion people in 2000 to 9.3 billion people in 2050. The UN estimates that the population will stabilize at more than 11 billion in 2200. Other e

7、xperts predict that numbers will continue to rise into the foreseeable future, to as many as 19 billion people by the year 2200. Although rates of population increase are now much slower in the developed world than in the developing world, it would be a mistake to assume that population growth is pr

8、imarily a problem of developing countries. In fact, because larger amounts of resources per person are used in developed nations, each individual from the developed world has a much greater environmental impact than does a person from a developing country. Conservation strategies that would not sign

9、ificantly alter lifestyles but that would greatly lessen environmental impact are essential in the developed world. In the developing world, meanwhile, the most important factors necessary to lower population growth rates are democracy and social justice. Studies show that population growth rates ha

10、ve fallen in developing areas where several social conditions exist. In these areas, literacy rates have increased and women receive economic status equal to that of men, enabling women to hold jobs and own property. In addition, birth control information in these areas is more widely available, and

11、 women are free to make their own reproductive decisions. B. Global Warming Like the glass panes in a greenhouse, certain gases in the Earths atmosphere permit the Suns radiation to heat Earth. At the same time, these gases retard the escape into space of the infrared energy radiated back out by Ear

12、th. This process is referred to as the greenhouse effect. These gases, primarily carbon dioxide, methane, nitrous oxide, and water vapor, insulate Earths surface, helping to maintain warm temperatures. Without these gases, Earth would be a frozen planet with an average temperature of about 18 instea

13、d of a comfortable 15 . If the concentration of these gases rises, they trap more heat within the atmosphere, causing worldwide temperatures to rise. Within the last century, the amount of carbon dioxide in the atmosphere has increased dramatically, largely because people bum vast amounts of fossil

14、fuels-coal and petroleum and its derivatives. Average global temperature also has increased-by about 0.6 Celsius degree within the past century. Atmospheric scientists have found that at least half of that temperature increase can be attributed to human activity. They predict that unless dramatic ac

15、tion is taken, global temperature will continue to rise by 1.4 to 5.8 Celsius degrees over the next century. Although such an increase may not seem like a great difference, during the last ice age the global temperature was only 2.2 Celsius degrees cooler than it is presently. The consequences of su

16、ch a modest increase in temperature may be devastating (破坏性的 ). Already scientists have detected a 40 percent reduction in the average thickness of Arctic ice. Other problems that may develop include a rise in sea levels that will completely inundate a number of low-lying island nations and flood ma

17、ny coastal cities, such as New York and Miami. Many plant and animal species will probably be driven into extinction, agriculture will be severely disrupted in many regions, and the frequency of severe hurricanes and droughts will likely increase. C. Depletion of the Ozone Layer The ozone (臭氧 ) laye

18、r, a thin band in the stratosphere (layer of the upper atmosphere), serves to shield Earth from the Suns harmful ultraviolet rays. In the 1970s, scientists discovered that chlorofluorocarbons (CFCs)- chemicals used in refrigeration, air-conditioning systems, cleaning solvents, and aerosol sprays-des

19、troy the ozone layer. CFCs release chlorine into the atmosphere; chlorine, in turn, breaks down ozone molecules. Because chlorine is not affected by its interaction with ozone, each chlorine molecule has the ability to destroy a large amount of ozone for an extended period of time. The consequences

20、of continued depletion of the ozone layer would be dramatic. Increased ultraviolet radiation would lead to a growing number of skin cancers and cataracts (白内障 ) and also reduce the ability of immune systems to respond to infection. Additionally, growth of the worlds oceanic plankton, the base of mos

21、t marine food chains, would decline. Plankton (浮游生物 ) contains photosynthetic organisms that break down carbon dioxide. If plankton populations decline, it may lead to increased carbon dioxide levels in the atmosphere and thus to global warming. Recent studies suggest that global warming, in turn, m

22、ay increase the amount of ozone destroyed. Even if the manufacture of CFCs is immediately banned, the chlorine already released into the atmosphere will continue to destroy the ozone layer for many decades. In 1987 an international pact called the Montral Protocol on Substances that Deplete the Ozon

23、e Layer set specific targets for all nations to achieve in order to reduce emissions of chemicals responsible for the destruction of the ozone layer. Many people had hoped that this treaty would cause ozone loss to peak and begin to decline by the year 2000. In fact, in the fall of 2000, the hole in

24、 the ozone layer over Antarctica was the largest ever recorded. The hole the following year was slightly smaller, leading some to believe that the depletion of ozone had stabilized. D. Habitat Destruction and Species Extinction Plant and animal species are dying out at an unprecedented rate. Estimat

25、es range that from 4,000 to as many as 50,000 species per year become extinct. The leading cause of extinction is habitat destruction, particularly of the worlds richest ecosystems-tropical rain forests and coral reefs. If the worlds rain forests continue to be cut down at the current rate, they may

26、 completely disappear by the year 2030. In addition, if the worlds population continues to grow at its present rate and puts even more pressure on these habitats, they might well be destroyed sooner. E. Air Pollution A significant portion of industry and transportation burns fossil fuels, such as ga

27、soline. When these fuels burn, chemicals and particulate matter are released into the atmosphere. Although a vast number of substances contribute to air pollution, the most common air pollutants contain carbon, sulfur, and nitrogen. These chemicals interact with one another and with ultraviolet radi

28、ation in sunlight in dangerous ways. Smog, usually found in urban areas with large numbers of automobiles, forms when nitrogen oxides react with hydrocarbons in the air to produce aldehydes (乙醛 ) and ketones (酮 ). Smog can cause serious health problems. Acid rain forms when sulfur dioxide and nitrou

29、s oxide transform into sulfuric acid and nitric acid in the atmosphere and come back to Earth in precipitation. Acid rain has made numerous lakes so acidic that they no longer support fish populations. Acid rain is also responsible for the decline of many forest ecosystems worldwide, including Germa

30、nys Black Forest and forests throughout the eastern United States. F. Water Pollution Estimates suggest that nearly 1.5 billion people worldwide lack safe drinking water and that at least 5 million deaths per year can be attributed to waterborne diseases. Water pollution may come from point sources

31、or nonpoint sources (非点污染源 ). Point sources discharge pollutants from specific locations, such as factories, sewage treatment plants, and oil tankers. The technology exists to monitor and regulate point sources of pollution, although in some areas this occurs only sporadically. Pollution from nonpoi

32、nt sources occurs when rainfall or snowmelt moves over and through the ground. As the runoff moves, it picks up and carries away pollutants, such as pesticides and fertilizers, depositing the pollutants into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. Pol

33、lution arising from nonpoint sources accounts for a majority of the contaminants in streams and lakes. 2 Global warming, the depletion of the ozone layer in the atmosphere, and destruction of the worlds rain forests have made up of all the environmental problems. （ A） Y （ B） N （ C） NG 3 The human po

34、pulation growth is the causes of all of the environmental problems. （ A） Y （ B） N （ C） NG 4 The worlds population will increase in 2000 to 9.3 billion people. （ A） Y （ B） N （ C） NG 5 The greenhouse effect is sure to cause a higher global temperature next century. （ A） Y （ B） N （ C） NG 6 The most imp

35、ortant factors necessary to lower population growth rates in the developing world are _. 7 The average thickness of Arctic ice has now been reduced by _. 8 The layer that serves to shield Earth from the Suns harmful ultraviolet rays is called _. 9 Increased ultraviolet radiation would lead to a grow

36、ing number _. 10 Acid rain has made numerous lakes so acidic that they _. 11 When rainfall or snowmelt moves over and through the ground, there will be _. 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

37、 questions will be asked about what was said. Both the conversation and the questions will be spoken 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） To persuade Margaret to spend mo

38、re time on her lessons. （ B） To help Margaret to prepare for the upcoming concert. （ C） To talk with Margaret about the concert she appreciates. （ D） To ask Margaret to stop worrying about the exam. （ A） Most people like to go to the museum. （ B） 10 a.m. is too late to visit the museum. （ C） There m

39、ight not be many who want to see the museum. （ D） The museum might not be open on weekends. （ A） Customer and shop assistant. （ B） Job applicant and interviewer. （ C） Student and teacher. （ D） Client and lawyer. （ A） Hes just seen a film. （ B） Hes just returned from a job interview. （ C） Hes going t

40、o a dance. （ D） Hes going to a party. （ A） Its one of his unreasonable ideas. （ B） Its an example of bad planning. （ C） It has turned out a failure for lack of funding. （ D） It has turned out fairly successful. （ A） The library. （ B） The research center. （ C） The theatre. （ D） The laboratory. （ A） T

41、he working hours were unsuitable. （ B） The job was not well paid. （ C） He had to do a lot of traveling. （ D） He didnt want to be a travel agent. （ A） The results might be ready tomorrow. （ B） The man needs another blood test tomorrow. （ C） The blood is being tested now in the lab. （ D） The doctor wi

42、ll be back tomorrow. （ A） To make sure that blind people have the same rights as everyone else. （ B） To provide the blind with a white lane for cross a street. （ C） To encourage people to volunteer to help the blind. （ D） To draw attention to the blind with a cane or a dog in crossing the street. （

43、A） It depends on their age. （ B） It depends on where they live. （ C） Its a matter of personal choice. （ D） Its a matter of social custom. （ A） When they are walking alone in the street. （ B） When they are trying to locate a chair. （ C） When they do not have a cane or dog. （ D） When there is construc

44、tion or a lot of noise around. （ A） The entertainment on campus. （ B） The entertainment facilities students use in town. （ C） The kinds of films and plays students enjoy. （ D） The cinemas and theatres students like to go to. （ A） The ticket prices were flat. （ B） The students go to both. （ C） They w

45、ere both modem. （ D） They offer the same performances. （ A） In April and May. （ B） In June and July. （ C） Around November and December. （ D） None of them. （ A） The service the cinemas and theatres offered. （ B） The ticket fares the students could afford. （ C） The variety of seat prices. （ D） The typ

46、es of performance. 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 choose the best answer from the four choices marked A,

47、B, C and D. （ A） Parents are more influential than teachers in childrens education. （ B） Parents are ignorant in making the most of their childrens intelligence. （ C） Parents are not advised to educate their children before school. （ D） Parents find it easiest to teach their children to read at home

48、. （ A） Five. （ B） Six. （ C） Seven. （ D） Eight. （ A） Language. （ B） Art. （ C） Natural Sciences. （ D） Physical culture. （ A） Advantages and disadvantages of freezers. （ B） The best energy-efficient freezer. （ C） Defrosting a manual defrost freezer. （ D） Choosing and caring for a freezer. （ A） They are

49、 more convenient. （ B） Their storage space is more accessible. （ C） They are more energy-efficient. （ D） They take up less floor area. （ A） Keep it away from heat, drafts, and humidity. （ B） Keep it as empty as possible. （ C） Wash its interior frequently. （ D） Set it regularly at zero degree. （ A） At the age of two. （ B） At the age of four. （ C） At the age of five. （ D） At the age of eight. （ A） The meals that her family enjoyed in Iran. （ B） The generosity that relatives gave them. （ C）