[外语类试卷]大学英语四级模拟试卷461及答案与解析.doc

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1、大学英语四级模拟试卷 461及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed thirty minutes to write a composition on the topic: Man and Environment-Problems and Solutions. You should write at least 120 words following the outline given below in Chinese: 1. 人类与环境关系密切； 2. 我们的环境面临着危机 (提示：污染，土壤

2、沙化，动植物灭绝等 )； 3. 必须采取切实有效的措施以保护我们的环境。 Man and Environment-Problems and Solutions 二、 Part II Reading Comprehension (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 1-7,

3、 mark： Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Nuclear power plants provide about 17 percent of the worlds electri

4、city. Some countries depend more on nuclear power for electricity than others. In France, for instance, about 75 percent of the electricity is generated from nuclear power, according to the International Atomic Energy Agency. In the United States, nuclear power supplies about 15 percent of the elect

5、ricity overall, but some states get more power from nuclear plants than others. There are more than 400 nuclear power plants around the world, with more than 100 in the United States. Have you ever wondered how a nuclear power plant works or how safe nuclear power is? In this article, we will examin

6、e how a nuclear reactor and a power plant work. Uranium Uranium is a fairly common element on Earth, which was taken into the planet during the planets formation. Uranium is originally formed in stars. Old stars exploded, and the dust from these shattered stars aggregated together to form our planet

7、. Uranium-238 (U-238) has an extremely long life (4.5 billion years), and therefore is still present in fairly large quantities. U-238 makes up 99 percent of the uranium on the planet. U-235 makes up about 0.7 percent of the remaining uranium found naturally, while U-234 is even rarer and is formed

8、by the decay of U-238. Nuclear Fission (裂变 ) A nuclear fission happens when a uranium-235 nucleus with a neutron captures another neutron. The nucleus then splits into two lighter atoms and throws off two or three new neutrons (the number of ejected neutrons depends on how the U-235 atom happens to

9、split). The two new atoms then produce gamma radiation as they settle into their new states. There are three things about this induced fission process that make it especially interesting: The probability of a U-235 atom capturing a neutron as it passes by is fairly high. In a reactor working properl

10、y (known as the critical state) , one neutron ejected from each fission causes another fission to occur. The process of capturing the neutron and splitting happens very quickly, on the order of picoseconds ( 11012seconds). An incredible amount of energy is released, in the form of heat and gamma rad

11、iation, when a single atom splits. The two atoms that result from the fission later release beta radiation and gamma radiation of their own as well. The energy released by a single fission comes from the fact that the fission products and the neutrons, together, weigh less than the original U-235 at

12、om. The difference in weight is converted directly to energy at a rate governed by the equation E = mc2. In order for these properties of U-235 to work, a sample of uranium must be enriched so that it contains 2 percent to 3 percent or more of uranium-235. Three-percent enrichment is sufficient for

13、use in a civilian nuclear reactor used for power generation. Weapons-grade uranium is composed of 90-percent or more U-235. Inside a Nuclear Power Plant To build a nuclear reactor, what you need is some mildly enriched uranium. Typically, the uranium is formed into pellets (芯块 ) with approximately t

14、he same diameter as a coin and a length of an inch or so. The pellets are arranged into long rods, and the rods are collected together into bundles. The bundles are then typically submerged in water inside a pressure vessel. The water is used to lower the heat. In order for the reactor to work, the

15、bundle, submerged in water, must be slightly supercritical. That means that, left to its own devices, the uranium would eventually overheat and melt. To prevent this, control rods (棒 ) made of a material that absorbs neutrons are inserted into the bundle. Raising and lowering the control rods allow

16、operators to control the rate of the nuclear reaction. When an operator wants the uranium core to produce more heat, the rods are raised out of the uranium bundle. To create less heat, the rods are lowered into the uranium bundle. The rods can also be lowered completely into the uranium bundle to sh

17、ut the reactor down in the case of an accident or to change the fuel. The uranium bundle acts as an extremely high-energy source of heat. It heats the water and turns it to steam. The steam drives a steam turbine, which spins a generator to produce power. In some reactors, the steam from the reactor

18、 goes through a secondary, intermediate heat exchanger to convert another loop of water to steam, which drives the turbine. Outside a Nuclear Power Plant Once you get past the reactor itself, there is very little difference between a nuclear power plant and a coal-fired or oil-fired power plant exce

19、pt for the source of the heat used to create steam. The reactors pressure vessel is typically housed inside a concrete liner that acts as a radiation shield. That liner is housed within a much larger steel containment vessel. This vessel contains the reactor core as well the hardware that allows wor

20、kers at the plant to refuel and maintain the reactor. The steel containment vessel is intended to prevent leakage of any radioactive gases or fluids from the plant. Finally, the containment vessel is protected by an outer concrete building that is strong enough to survive such things as crashing jet

21、 airliners. These secondary containment structures are necessary to prevent the escape of radiation/radioactive steam in the event of an accident like the one at Three Mile Island. The absence of secondary containment structures in Russian nuclear power plants allowed radioactive material to escape

22、in an accident at Chernobyl. What Can Go Wrong Well-constructed nuclear power plants have an important advantage when it comes to electrical power generation-they are extremely clean. Compared with a coal-fired power plant, nuclear power plants are a dream come true from an environmental standpoint.

23、 A coal-fired power plant actually releases more radioactivity into the atmosphere than a properly functioning nuclear power plant. Coal-fired plants also release tons of carbon, sulfur and other elements into the atmosphere. Unfortunately, there are significant problems with nuclear power plants: M

24、ining and purifying uranium has not, historically, been a very clean process. Improperly functioning nuclear power plants can create big problems. The Chernobyl disaster is a good recent example. Spent fuel from nuclear power plants is toxic (有毒的 ) for centuries, and, as yet, there is no safe, perma

25、nent storage facility for it. Transporting nuclear fuel to and from plants poses some risk, although to date, the safety record in the United States has been good. These problems have largely derailed the creation of new nuclear power plants in the United States. Society seems to have decided that t

26、he risks outweigh the rewards. 2 There are over 00 hundred nuclear power plants in the world, most of the them are in Europe. （ A） Y （ B） N （ C） NG 3 Scientists believe that uranium was absorbed by the Earth when it was formed. （ A） Y （ B） N （ C） NG 4 The German government has decided to reduce its

27、dependence on electricity generated by nuclear power. （ A） Y （ B） N （ C） NG 5 A nuclear fission is a process of a U-23 nucleus with a neutron trying to capture another neutron. （ A） Y （ B） N （ C） NG 6 Uranium has to be enriched if a nuclear reactor is built. （ A） Y （ B） N （ C） NG 7 Control rods in a

28、 nuclear reactor are used to control the amount of energy generated in a nuclear reactor. They can also be used to shut the reactor or to change the fuel. （ A） Y （ B） N （ C） NG 8 Mining and purifying uranium do not cause any environmental damage. （ A） Y （ B） N （ C） NG 9 A nuclear reactor is protecte

29、d by _ , a concrete radiation shield, a steel containment vessel, and an outer concrete building. 10 The result of nuclear fission is to release energy in the form of _. 11 The present solution to dispose _ is yet to be found as it remains toxic for a fairly long time. Section A Directions: In this

30、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 spoken only once. After each question there will be a pause. During the pause, you must rea

31、d the four choices marked A, B, C and D, and decide which is the best answer. （ A） Outside a bookstore. （ B） At a stop sign. （ C） Near a sports park. （ D） In front of a library. （ A） She wanted to get ready for the party. （ B） She was afraid of going out at night. （ C） She had to be home early. （ D）

32、 She wanted to get ready for the play. （ A） The local people help the government with nature protection. （ B） The leaders are enjoying an opera with the local people. （ C） The villagers are running business. （ D） The local government is doing everything it could to preserve natural resources. （ A） S

33、he needs to get more rest. （ B） She took a rest last week and it helped her a lot. （ C） She wasnt interested in last weeks lecture. （ D） She was surprised to find the lecture so easy. （ A） The lawn needs cutting. （ B） The lawn helps cool her house. （ C） She needs more air conditioning. （ D） Her hous

34、e is beautiful. （ A） He doesnt agree with the woman. （ B） He agrees with the woman. （ C） The newspaper is responsible for environmental protection. （ D） The newspaper has much to do with the environment. （ A） He cant stand up. （ B） He feels the same way as the woman. （ C） He is not a doctor, either.

35、 （ D） He will not stand in the way. （ A） They are talking about the world. （ B） They met some time ago. （ C） They are discussing how small the world is. （ D） They dont want to meet again. （ A） English. （ B） American. （ C） Australian. （ D） Canadian. （ A） The difference of meaning. （ B） The difference

36、 of pronunciation. （ C） The difference of some vocabulary. （ D） The extent of the difference. （ A） After half of the movie was over. （ B） Before half of the movie was over. （ C） After the movie was over. （ D） After he was told by a classmate. （ A） Where it is. （ B） When it is open. （ C） How she can

37、go there. （ D） What she can see there. （ A） 3.00. （ B） 3.50. （ C） 4.00. （ D） 4.50. （ A） Bells and masks. （ B） Clocks and masks. （ C） Clocks and swords. （ D） Bells and swords. （ A） Oct. 9. （ B） Nov. 11. （ C） Sep. 8. （ D） Dec. 12. Section B Directions: In this section, you will hear 3 short passages.

38、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, B, C and D. （ A） Because everyone knows you in a new place. （ B） Because your old friends

39、arent watching you. （ C） Because you have much pressure of your former colleagues. （ D） Because you have more opportunities. （ A） You cant find a good job. （ B） You may waste a lot of time. （ C） You may feel lonely and unhappy at the beginning. （ D） You have to leave your children. （ A） Children are

40、 always happy to move to a new city. （ B） Moving brings the opportunities as well as some problems. （ C） Husband and wife dont matter if he or she can benefit from the move. （ D） You should think about the future when you move. （ A） Drug. （ B） Substance. （ C） Medicine. （ D） Alcohol. （ A） They will p

41、roduce negative effects. （ B） They will produce positive effects. （ C） They will produce no effects. （ D） They will produce the desired effects. （ A） Mental addiction. （ B） Substance independence. （ C） The desired effects. （ D） Substance dependence （ A） The great numbers of people engaged in cigaret

42、te producing. （ B） The rapid development of cigarette-making machine. （ C） The rapid development of cigarette-making factories. （ D） The increasing output of tobacco. （ A） Forty-three. （ B） Thirty-one. （ C） Seventy-five. （ D） Forty-six. （ A） Income, years of schooling, and job type. （ B） Income and

43、work environment. （ C） Education and mood. （ D） Occupation and influence of family members. （ A） Under 18. （ B） Under 16. （ C） Over 19. （ D） Under 17. Section C Directions: In this section, you will hear a passage three times. When the passage is read for the first time, you should listen carefully

44、for its general idea. When the passage is read for the second time, you are required to fill in the blanks numbered from 36 to 43 with the exact words you have just heard. For blanks numbered from 44 to 46 you are required to fill in the missing information. For these blanks, you can either use the

45、exact words you have just heard or write down the 36 One night in April 1912, a huge new【 B1】 _liner, the Titanic, was【 B2】 _the Atlantic. She was just about the most【 B3】 _ship that had ever been built. She was going very fast, which was【 B4】 _because there were icebergs around and it was very dark

46、 that night. The【 B5】 _were all having a good time when the ship suddenly【 B6】 _one of the icebergs. The ship began to【 B7】 _and the passengers tried to【 B8】 _, but there were not enough lifeboats since nobody thought they would ever be necessary. Eight white rockets were fired into the air in order

47、 to get help. Another ship, the Californian, was passing nearby. An officer and another sailor on it saw the rockets.【 B9】 _. Anyway they did wake the captain. But the captain was too sleepy to understand and the Californian just went on sailing away, in another direction. When the Titanic finally w

48、ent down,【 B10】 _. They were trying to keep the passengers calm. Two thirds of the passengers were drowned.【 B11】 _. 37 【 B1】 38 【 B2】 39 【 B3】 40 【 B4】 41 【 B5】 42 【 B6】 43 【 B7】 44 【 B8】 45 【 B9】 46 【 B10】 47 【 B11】 Section A Directions: In this section, there is a passage with ten blanks. You are

49、 required to select one word for each blank from a list of choices given in a word bank following the passage. Read the passage through carefully before making your choices. Each choice in the bank is identified by a letter. Please mark the corresponding letter for each item with a single line through the center. You may not use any of the words in the bank more than once. 47 A subject which seems to have been insufficiently studied by doctors. tom and psychologists is t