[外语类试卷]大学英语四级模拟试卷849及答案与解析.doc

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1、大学英语四级模拟试卷 849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 Students Use of the Net. You should write at least 120 words and you should base your composition on the outline (given in Chinese ) below: Students Use of the Net

2、1近年来，大学生上网时间呈急剧上升趋势。上图所示为 1995年、 2000年、 2005年某校大学生上网时间的变化情况，请对其进行描述； 2请分析发生这些变化的原因 (可从网络设施、用途或社会发展方面进行说明 )； 3你的看法 (从利弊角度来谈 )。 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 questio

3、ns attached to the passage. For questions 1-7, 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 New Hope, Old Fears B

4、onnie Krull, 54, had already had enough breast-caner scares for one lifetime, with a few to spare for reincarnations (再生 ). Her great-aunt, aunt, mother and sister all developed the disease. A few years ago Krull herself, a telecom manager in Los Angeles and a mother of two grown sons, was being pre

5、pped for surgery for what her doctor concluded was a malignancy (恶性肿瘤 ) in her left breast. As she underwent a final mammogram so the surgeon could pinpoint where to cut, and with the already dripping, the radiologist suddenly muttered that the lump had vanished. Heartened for the clinical trial of

6、tamoxifen, a drug that preliminary data suggested might prevent breast cancer. Last week federal health officials announced at a press conference results that convinced Krull, who by chance was in the group receiving tamoxifen rather than a placebo, that her luck was holding. Among the 13,388 high-r

7、isk women in the trial, tamoxifen reduced the incidence of breast cancer a full 45 percent. “I really believe that tamoxifen saved me,“ says Krull, “and that I am going to be the one who breaks the link in the family chain of cancer.“ Normally circumspect scientists were no less euphoric (愉快的 ). “Fo

8、r the first time we have demonstrated that one can alter the incidence of breast cancer,“ says Dr. Norman Wolmark, chairman of the National Surgical Adjuvant Breast and Bowel Project at Allegheny University of the Health Sciences, which ran the tamoxifen trial, and not just by tinkering at the margi

9、ns. The 45 percent lower incidence Of invasive breast cancer among women receiving tamoxifen-85 cases compared to 154-was so stark that, in a controversial decision, the researchers ended the study 14 months ahead of schedule. The results were not all positive, though. The women on tamoxifen, who to

10、ok two 10-milligram pills each day, also had 33 cases of endometrial cancer versus 14 in the placebo group, 17 cases of pulmonary embolism (potentially fatal blood clots in the lung) compared with six among the women on a placebo and 30 cases of dangerous lung clots in major veins compared with 19 i

11、n the placebo group. Tamoxifen, clearly, is not the silver bullet that will kill breast cancer. “This is not primarily about tamoxifen,“ says oneologist Nikolay Dimitrov of Michigan State University. “This is a proof of the concept that prevention works. Now we can look for new chemopreventives with

12、out the side effects of tamoxifen.“ Other such drugs are in the pipeline. Researchers hope to begin a clinical trial on one, raloxifene, as early as this fall. Made by Eli Lilly and Co., raloxifene serendipitously turned out to lower the incidence of breast cancer among women on whom it was being te

13、sted against osteoporosis. Until the perfect preventive comes along, should women at high risk for breast cancer ask their doctors for tamoxifen? (Because tamoxifen has been used for more than 20 years as a breast cancer treatment, doctors can prescribe it for such “off-label“ uses as prevention, bu

14、t government approval of such a use is at least six months away.) Many worried women are considering it. Karen Recht, a gift-shop manager in Wheeling, W. Va. , was in the tamoxifen trial. As chance would have it, she received the placebo. Recht, 57, volunteered because she wanted to help “the two li

15、ttle girls my sister (who died of breast caner at 45) left behind. I never dreamed I would benefit. But now Im very tempted to try tamoxifen. I feel like it will give me five more years in which I wont get breast cancer.“ The results announced last week apply just to high-risk women, the only kind p

16、articipating in the study. For women at low risk for breast cancer, there is no evidence that the benefits of tamoxifen outweigh the dangers. “High risk“ was defined as having the same chance of getting breast cancer as a 60-year-old American woman: a 1.7 percent chance of getting the disease within

17、 five years. Besides age, other risk factors include having a mother, daughter or sister with breast caneer; having a first child after age 30; having had breast biopsies, especially if the tissue turned out to be precancerous, and having the noninvasive breast cancer called lobular carcinoma in sit

18、u. Some 29 million American women meet this definition of high risk, including 3 million between 35 and 59. “But we need to be very cautious,“ says Dr. Patricia Ganz of UCLAs Jonsson Comprehensive Cancer Center. “Tamoxifen might not be appropriate even for every highrisk women.“ Thats because a 45 p

19、ercent reduction in the incidence of breast cancer is huge, but it is not 100 percent. Why did 85 women on tamoxifen still get breast cancer (and, in three cases, die of it)? One clue comes from the biochemistry of the compound. First synthesized in 1961 by chemist Dora Richardson, for Zeneca Pharma

20、ceuticals, tamoxifen is an anti-estrogen (雌激素 ). It binds to receptors on the nuclei of breast cells. Receptors are like loading docks, specially shaped molecules on which estrogen circulating in the blood parks before getting transported right into the nucleus. There, estrogen turns on a suite of g

21、enes, including those for cell proliferation. But tamoxifen hogs the estrogen receptors. That leaves no spots for estrogen itself to dock and hence turn on the proliferation genes. Not all breast cancers have estrogen receptors, however. “In postmenopausal women, about 75 to 80 percent of the cancer

22、s are estrogen dependent,“ says UCLAs Ganz. “But in younger women its only about 35 or 40 percent.“ Women whose cancers are not estrogen-sensitive are usually not prescribed tamoxifen as chemotherapy. “One reason tamoxifen did not prevent breast cancer in every woman might be that these women had es

23、trogen-receptor-negative cells,“ suggests V. Craig Jordan of Northwestern Universitys Lurie Cancer Center, who in 1973 first discovered that tamoxifen can prevent cancer in lab animals. One research priority is to figure out what determines whether a woman develops cancer cells with or without estro

24、gen receptors. Another question is whether tamoxifen can help women who carry mutations in the BRCA1 or BRCA2 genes. When the tamoxifen trial began in April 1992, geneticists had not yet discovered these so-called “breast-cancer genes,“ which (with other hypothesized genes) account for some 7 percen

25、t of all cases of the disease. But DNA samples were taken from every woman in the trial. It should therefore be possible to go back and, by matching the BRCA status of each woman to how she fared on tamoxifen, figure out whether tamoxifen can prevent cancer in these highest-risk women. On paper, it

26、might. “Estrogen turns on a whole host of genes inside the breast cell,“ says Dr. Brian Henderson of the Norris Comprehensive Cancer Center at the University of Southern California, “possibly including BRCA1. If we can dam up the effects of estrogen upstream by blocking them with tamoxifen or some o

27、ther compound, you will never suffer from BRCA1.“ It is not clear whether tamoxifen helps younger or older women more. As UCLAs Ganz points out, older women are more likely to have estrogen-sensitive cells whose proliferation tamoxifen can quash. So tamoxifen might be expected to be more effective f

28、or them. In the trial, tamoxifen indeed provided slightly more benefit to women over the age of 50: it prevented 17 cases of invasive breast cancer, out of the 33 cases expected without the drug. Among those 35 to 49, it prevented 14 cases out of the 31 expected. But the older women were also at gre

29、ater risk for such serious side effects as endometrial cancer and blood clots in the lungs and veins. Tamoxifen had no effect on endometrial cancer or blood clots in younger women. 2 The passage gives a general description of tamoxifen which cures cancer. （ A） Y （ B） N （ C） NG 3 Bonnie Krull and her

30、 female relatives all developed breast cancer. （ A） Y （ B） N （ C） NG 4 Tamoxifen is the most effective drug to cure breast cancer. （ A） Y （ B） N （ C） NG 5 Tamoxifen is appropriate for every high-risk woman. （ A） Y （ B） N （ C） NG 6 85 women on tamoxifen still get breast cancer partly because of the b

31、iochemistry of the compound. （ A） Y （ B） N （ C） NG 7 All breast cancers have estrogen receptors. （ A） Y （ B） N （ C） NG 8 In the trial, tamoxifen indeed provided slightly more benefit to women over the age of 50. （ A） Y （ B） N （ C） NG 9 Researchers hope to begin _. 10 For women at low risk for breast

32、 cancer, _. 11 As UCLAs Ganz points out, older women _. 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 spoke

33、n 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） He was very sad. （ B） He was very angry. （ C） He was very nervous. （ D） He was very happy. （ A） He has some money to buy a new car.

34、 （ B） He wants to buy a new house and a new car. （ C） He will spend much money on his house. （ D） He fails in borrowing enough money from the woman. （ A） It is in heavens name. （ B） It disappeared. （ C） It got broken. （ D） It is overweight. （ A） The cause of the flood. （ B） The effects of the flood.

35、 （ C） The heroic fight against a flood. （ D） Floods of the past twenty years. （ A） He thinks hes taken too few courses. （ B） He thinks hes taken too ninny courses. （ C） He doesnt think he has taken enough courses. （ D） He thinks the number of the courses hes taken is just right. （ A） She thinks the

36、show is dull. （ B） She thinks the show is moving. （ C） She considers the show is inspiring; （ D） She considers the show is enjoyable. （ A） Its bigger than he has imagined. （ B） Its much more brighter. （ C） Its smaller than he has thought. （ D） Its full of furniture. （ A） The “Mirror“ and “The Sun“.

37、（ B） Low-quality papers. （ C） The major national dailies. （ D） All kinds of newspapers. （ A） Searching for reference material., （ B） Watching a film of the 1930s. （ C） Writing a course book. （ D） Looking for a job in a movie studio. （ A） Its too broad to cope with. （ B） Its a bit outdated. （ C） Its

38、controversial, （ D） Its of little practical value. （ A） At the end of the online catalogue. （ B） At the Reference Desk. （ C） In the New York Times. （ D） In the Readers Guide to Periodical Literature. （ A） It is weird. （ B） It is exhausting. （ C） It is convenient. （ D） It is comfortable. Section B Di

39、rections: 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, B, C and D. （ A） A solution to

40、mans food problem. （ B） A solution to the population problem. （ C） Advantages of soybean. （ D） How to develop good eating habits. （ A） Because people have to spend too much time and energy to produce it. （ B） Because too much grain protein is needed to produce it. （ C） Because it contains too much f

41、at and protein. （ D） Because it is not good to the health. （ A） It is similar to real meat in appearance but not in taste. （ B） It is similar to real meat neither in appearance nor in taste. （ C） It is similar to real meat both in appearance and in taste. （ D） It is similar to real meat in taste, bu

42、t not in appearance. （ A） He took them to watch a basketball game. （ B） He trained them to play European football. （ C） He let them compete in getting balls out of a basket. （ D） He taught them to play an exciting new game. （ A） The players found the basket too high to reach. （ B） The players had tr

43、ouble getting the ball out of the basket. （ C） The players had difficulty understanding the complex rules. （ D） The players soon found the game boring. （ A） By removing the bottom of the basket. （ B） By lowering the position of the basket. （ C） By simplifying the complex rules. （ D） By altering the

44、size of the basket. （ A） Failure and success. （ B） The “spider-story“. （ C） Two sides of failure. （ D） The invention of the light bulb. （ A） Failure must come before success. （ B） Failure is not all bad. （ C） Failures can be avoided. （ D） Failures are unavoidable. （ A） You should check out your goal

45、s to see if they are right for us. （ B） You should regard failure as a part of life. （ C） You should think of failure to find out what has gone wrong. （ D） You should give up trying when the failure keeps occurring. （ A） We should not think about it any more. （ B） We should take it easy. （ C） We sho

46、uld discuss it with other. （ D） We should learn to accept it. 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 for its general idea. When the passage is read for the second time, you are required to f

47、ill 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 exact words you have just heard or write down the 33 The first flight of the Space Shuttl

48、e Columbia in the spring of 1981 was a revolutionary development in space【 B1】 _. Unlike the rockets of the previous 20 years, Columbia has the【 B2】 _advantage of being specially designed to return to earth and make【 B3】 _flights. Among the large number of projects scientists are【 B4】 _for its futur

49、e use, the most exciting, perhaps, is that the first steps can now be taken towards【 B5】 _human【 B6】 _in space. The present Space Shuttle can only stay in space for about a week, but it could take people out to【 B7】_ “islands“ where they stay for longer periods. By the year 2050, scientists estimate that man will be able to construct permanent【 B8】 _ The first “islands“ would be energy stations.【 B9】 _. However, if the original could【 B10】 _, allowing the Spa