大学英语六级274及答案解析.doc

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1、大学英语六级 274及答案解析(总分：428.04，做题时间：132 分钟)一、Part I Writing (3(总题数：1，分数：30.00)1.For this part, you are allowed 30 minutes to write a short essay entitled Should High School Students Study Abroad? You should write at least 150 words following the outline given below: （分数：30.00）_二、Part II Reading C(总题数：1，分

2、数：71.00)Animal tests More than a cosmetic (化妆品) change Every time you reach for an eye-drop or reapply a lip salve, you do be so confident that the chemicals they contain are safe to use. But the toxicology (毒物学) tests on which regulators rely to gather this information are largely based on wasteful

3、 and often poorly predictive animal experiments. Efforts in Europe are about to change this, and the man charged with bringing toxicology into the twenty-first century is a plain-talking German: Thomas Hartung. Although Hartung acknowledges the immense challenges ahead, he sees this as an opportunit

4、y for toxicology “to turn itself at last into a respectable science“. Three years ago, when Hartung became director of the European Centre for the Validation of Alternative Methods (ECVAM) in Ispra, Italy. ECVAM was set up in 1993 to support European Union policy aimed at reducing the number of anim

5、als used in regulatory testing. The centre, which sits on the sleepy shores of Lake Maggiore in the Italian Alps, originally had ten members of staff and faced an uphill struggle to cut back the millions of animal tests carried out in Europe every year. Then in 2003, two major policy changes were an

6、nounced from above, increasing the pressure on the centres labs. ECVAM found itself facing an unexpectedly short deadline for delivering a slew of animal-free methods for testing chemical toxicity. Rule change The first change was to the European Unions Cosmetics Directive, which phases out over ten

7、 years the use of animals in cosmetics testing. A short while later, the European Commission proposed its controversial REACH legislation (Registration, Evaluation and Authorization of Chemicals). Europe produces some 30,000 chemicals for which toxicity data have never been registered. REACH aims to

8、 make registration mandatory for both future and existing chemicals even those that have been on the market for decades. If, as expected, the REACH directive is approved next year, it will come into effect in 2007. Animal-welfare groups fear that this will mean millions more animals will be used in

9、tests to meet the regulatory requirements. And industry claims that the testing process could cost billions of euros. Almost overnight, industrys interest in cheaper, animal-free testing skyrocketed. Last month ECVAM was put in charge of developing, with industry and regulatory agencies, the testing

10、 strategies for REACH. Now commanding 50 staff, Hartung is rising to the challenge. “The toxicity tests that have been used for decades are simply bad science“, he explains. “We now have an opportunity to start with a clean slate and develop evidence-based tests that have true predictive value.“ Man

11、y of the animal tests used today were developed under crisis conditions. The notorious Draize test, which assesses the irritation or damage caused by chemicals simply by putting them into the eyes of rabbits, is a prime example. It was developed by the US Food and Drug Administration in 1944 after r

12、eports in the 1930s that some cosmetics were causing permanent eye injuries. One 38-year-old woman had gone blind after dyeing her lashes with Lash-Lure, a product that contained a derivative of coal tar. Then came the calamity of thalidomide (镇静剂), which was given to pregnant women in the late 1950

13、s to control morning sickness, but which caused horrific birth defects. By this time, governments were highly sensitive to public concerns and called on their authorities to develop animal-based tests that would predict all conceivable toxic effects of drugs and chemicals. The principles behind most

14、 of those tests remain more or less unchanged today. Safety catch Each chemical that goes through the multiple tests required for registration can use up to 5,000 animals or 12,000 if the chemical is a pesticide. The cost of doing this for the 30,000 unregistered chemicals so that they comply with R

15、EACH has been estimated at between 5 billion (US$6 billion) and 10 billion. In the decade since ECVAM was established, the number of animals used in toxicology testing has fallen slightly, although it still hovers at about one million per year. This reduction is a result of the refinement of existin

16、g tests, and the introduction of some alternative methods that rely on in vitro (试管) tests using cell cultures. ECVAM believes that it can halve the total number of animals used for regulatory testing within a decade. It has just completed its first large-scale validation study of an in vitro cytoto

17、xicity test, which monitors death of cultured cells following short-term exposure to a chemical. Chemicals shown to be harmful in this test would be excluded from any LD50 animal tests. At least 70% of the chemicals registered in the past two decades fall into this category, says Hartung. And this i

18、s just the beginning. Poor prediction Most animal tests over-or under-estimate toxicity, or simply dont mirror toxicity in humans very well. The relevant industries also acknowledges the poor quality of those tests. Take the embryotoxicity test in which chemicals are fed to pregnant animals and the

19、fates of their embryos, and the progeny of two subsequent generations, are studied. “Animal embryotoxicity tests are not reliably predictive for humans,“ says Horst Spielmann, a toxicologist at the Federal Institute for Risk Assessment in Berlin. “When we find that cortisone is embryotoxic in all sp

20、ecies tested except human, what are we supposed to make of them?“ The same goes for cancer. To test a single chemical for its potential to cause cancer takes five years and involves 400 rats, each of which is treated with the maximum tolerated dose. It is dramatically over-predictive: more than 50%

21、of the results are positive, of which 90% are false positive. Yet the number of compounds proved to be carcinogenic to humans is very low the International Agency for Research on Cancer in Lyons, France, has identified just 95 proven and 66 probable human carcinogens (致癌物质). Life or death Scientists

22、 also cannot assume that in vitro alternatives are automatically better, says Spielmann. In 1971, a comparison of animal Draize tests in different labs revealed the test to be hopelessly non-reproducible. But Spielmanns 1995 study of animal-free alternatives to the Draize test showed that they were

23、equally unreliable. Since then the in vitro tests have been standardized, and they are intrinsically more reproducible. “Although reproducibility and relevance are not the same thing,“ Spielmann cautions. Relevance requires a good match between the test results and human data. At an ECVAM workshop i

24、n February, 30 industrial scientists met to develop the most effective strategy for using the alternative Draize tests, so that the false negatives and false positives of each test compensate for each other. This strategy is now going through the crucial validation procedure, in which human data, of

25、ten from occupational health databases, will be used as points of reference. ECVAM has so far seen 17 alternative tests through validation 11 use in vitro methods, another six involve refining in vivo tests to reduce the number of animals used. Most of the new tests assess acute toxicity, but animal

26、 use is highest when testing for the toxic effects of prolonged exposure to chemicals for long-term consequences such as cancer and reproductive toxicity. These costly procedures are harder to mimic in vitro and may never be completely replaced. Sounds familial This is why, apart from the 30 million

27、 it uses to support ECVAM annually, the European Commission is funding three multimillion-euro Integrated Projects. Under these, dozens of labs will collaborate for five years to tackle more difficult issues, such as allergic reactions (过敏反应) or widespread toxicity resulting from chemicals entering

28、the bloodstream. Scientists know that they are likely to find it hardest to convince regulators about alternative tests for highly emotive issues such as cancer and birth defects. More than half of all animals that will be needed to support REACH legislation are likely to be used in reproductive tox

29、icology testing. The 9-million Integrated Project called ReProTect has 27 labs dedicated to developing alternatives to these tests. The ReProTect consortium has broken down the human reproductive cycle into smaller elements, from male and female fertility to implantation, to pre-and postnatal develo

30、pment, and is trying to develop a meaningful package of tests. “Quite correctly everyone feels uneasy about taking risks where stakes are so high and issues so emotive,“ says Hartung. “We all want to be sure that there is real evidence that alternative tests are predictive of human toxicity.“ For ex

31、ample, regulators know the weaknesses of the rat cancer test as well as scientists but, wanting to be safe rather than sorry, they accept it because it is believed to throw up few false negatives. They prefer to let industry prove the innocence of any compound that shows up positive. Any replacement

32、 tests will need to reassure both regulators and industry. （分数：71.00）(1).Most toxicology tests for cosmetics are often poorly predictive animal experiments.（分数：7.10）A.YB.NC.NG(2).Thomas Hartung is an Italian.（分数：7.10）A.YB.NC.NG(3).European Unions Cosmetics Directive has 50 staff.（分数：7.10）A.YB.NC.NG(

33、4).According to Hartung, the toxicity tests used for tens of years are simply bad science.（分数：7.10）A.YB.NC.NG(5).Thalidomide used in the late 1950s to control morning sickness caused_.（分数：7.10）_(6).ECVAM believes that the refined in vitro test method can reduce by halve _used for regulatory testing

34、within a decade.（分数：7.10）_(7).How is an embryotoxicity test carried out?（分数：7.10）_(8).From the passage we know that results of cancer tests on animals are often_.（分数：7.10）_(9).Reproducibility and relevance differ in the sense that relevance requires_.（分数：7.10）_(10).Scientists think that they may fin

35、d it most difficult to persuade regulators to use alternative tests for_.（分数：7.10）_三、Listening Comprehens(总题数：1，分数：15.00)A.At Annes Clothing Store.B.Inside a shopping center.C.At a downtown street.D.In a suburban residential district.A.He was fired from his job.B.He was warned about being more punct

36、ual from now on.C.The management cut his working hours.D.He was promoted.A.They are at a violin shop.B.They are at a circus.C.They are at a concert.D.They are inside a movie theatre.A.She didnt go to work this morning.B.She was injured and had to go to the hospital.C.She talked with the boss in the

37、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.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

38、.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.C.His daughter was sick and that made him late for work.D.He prepared a financial report incorrectly.四、Section A(总题数：2，分数：10.00)A.Headache.B.Earache.C.Too

39、thache.D.Stomachache.A.Seafood.B.Roast beef.C.Ice-cream.D.Pancake.A.Dont eat any food for dinner.B.Dont be worry.C.Avoid oily food for the next few days.D.Should stay in hospital.A.To tell her that he cant attend her class today.B.To make an appointment with her for his roommate.C.To tell her that h

40、is roommate is unable to attend her class today.D.To discuss with her about his term paper.A.He almost forgets to hand in the term paper.B.He almost forgets to ask the location of Dr. Bauers office.C.He almost forgets to ask for the information of a course in next semester.D.He almost forgets to mak

41、e an appointment with Dr. Bauer.A.They have to take final exam.B.They have to give presentation.C.They have to read numerous books.D.They have to hand in a term paper of 2,000 words.五、Section B(总题数：3，分数：10.00)A.An Indian summer brings warm days and nights.B.An Indian summer occurs only in October.C.

42、An Indian summer is an annual phenomenon.D.An Indian summer lasts many weeks.A.The first period of cold, wintry days in autumn.B.The turning of color and falling of leaves.C.A large mass of warm tropical air carried northward.D.The southwestern winds.A.A short period of fair weather and mild days.B.

43、No definite time of beginning or ending.C.Its end signals winters start.D.Soft yellow or orange skies.A.Because he wanted to steal a violin and take it out with him.B.Because he was planning to commit a crime.C.Because he was going to earn money by playing his violin in the street.D.Because he was g

44、oing to return home.A.He stood in the middle of the payment.B.He stood under a bridge near the station.C.He stood on a bridge near the station.D.He stood in front of the station.A.He was full of confidence at his success.B.He felt like a circus performer.C.He felt as if he had been performing all hi

45、s life.D.He was determined to travel round the world.A.They are usually more clever.B.They get tired easily.C.They are more likely to make minor mental errors.D.They are more skillful in handling equipment.A.It had its limitations.B.Its results were regarded as final.C.It was supported by the govern

46、ment.D.It was not sound theoretically.A.Because we lose our acting ability then.B.Because we lose track of what we are doing then.C.Because we lose our thinking ability then.D.Not mentioned.A.Their lack of concentration resulting from mental stress.B.The lack of consideration for them in equipment d

47、esign.C.The probability of their getting excited easily.D.Their slowness in responding.六、Section C(总题数：1，分数：10.00)Giving birth to a child was a life-or-death struggle for the mother and baby as late as the early half of this century; an estimate survey ed a (36) 1 rate among mothers as high as 15 per thousand and infant as high as 200 per thousand at that time. Midwifery was practiced by the mother-in-law, the mother herself, or more (37) 2, by an elderly woman in the village who prac