大学六级-472及答案解析.doc

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1、大学六级-472 及答案解析(总分：687.00，做题时间：90 分钟)一、BPart Writing(总题数：1，分数：106.00)1.BHow to Deal with Personal Crisis/B1.造成个人危机的起因； 2.应对个人危机的方法。（分数：106.00）_二、BPart Reading (总题数：1，分数：70.00)BGENETICALLY MODIFIED FOODS/BAre genetically modified crops an environmental dream come-true or a disaster in the making? Scie

2、ntists are looking for answers.The world seems increasingly divided into those who favor genetically modified (GM) foods and those who fear them Advocates assert that growing genetically altered crops can be kinder to the environment and that eating foods from those plants is perfectly safe. And, th

3、ey say genetic engineering which can induce plants to grow in poor soils or to produce more nutritious foods will soon become an essential tool for helping to feed the worlds burgeoning population. Skeptics contend that GM crops could pose unique risks to the environment and to health risks too trou

4、bling to accept placidly, Taking that view, many European countries are restricting the planting and importation of GM agricultural products. Much of the debate hinges on perceptions of safety. But what exactly does recent scientific research say about the hazards? The answers, too often lost in rep

5、orts on the controversy, are served up in the pages that follow. Two years ago in Edinburgh, Scotland, eco-vandals stormed a field, crushing canola plants. Last year in Maine, midnight raiders hacked down more than 3000 experimental poplar trees. And in Sun Diego, protesters smashed sorghum and spra

6、yed paint over greenhouse walls.This far-flung outrage took aim at genetically modified crops. But the protests backfired: all the destroyed plants were conventionally bred. In each case, activists mistook ordinary plants for GM varieties.Its easy to understand why. In a way, GM cropsnow on some 109

7、 million acres of farmland worldwideare invisible. You cant see, taste or touch a gene inserted into a plant or sense its effects on the environment. You cant tell, just by looking, whether pollen containing a foreign gene can poison butterflies or fertilize plants miles away. That invisibility is p

8、recisely what worries people. How, exactly, will GM crops affect the environment-and when will we notice?Advocates of GM, or transgenic, crops say the plants will benefit the environment by requiting fewer toxic pesticides than conventional crops. But critics fear the potential risks and wonder how

9、big the benefits really are. “We have so many questions about these plants,“ remarks Guenther Stotzky, a soil microbiologist at New York University. “Theres a lot we dont know and need to find out.“As GM crops multiply in the landscape, unprecedented numbers of researchers have started fanning into

10、the fields to get the missing information. Some of their recent findings are reassuring; others suggest a need for vigilance.B Fewer Poisons in the Soil?/BEvery year U.S. growers shower crops with an estimated 971 million pounds of pesticides, mostly to kill insects, weeds and fungi. But pesticide r

11、esidues linger on crops and the surrounding soil, leaching into groundwater, running into streams and getting gobbled up by wildlife. The constant chemical trickle is an old worry for environmentalists.In the mid-1990s agribusinesses began advertising GM seeds that promised to reduce a farmers use o

12、f toxic pesticides. Today most GM crops-mainly soybean, com, cotton and canola-contain genes enabling them to either resist insect pests or tolerate weed-killing herbicides. The insect-resistant varieties make their own insecticide, a property meant to reduce the need for chemical sprays. The herbic

13、idetolerant types survive when exposed to broad-spectrum weed killers, potentially allowing farmers to forgo more poisonous chemicals that target specific weed species. Farmers to limit the use of more hazardous pesticides when they can, but GM crops also hold appeal because they simplify operations

14、 ( reducing the frequency and complexity of pesticide applications) and, in some cases, increase yields.But confirming environmental benefit is tricky. Virtually no peer-reviewed papers have addressed such advantages, which would be expected to vary from plant to plant and place to place. Some infor

15、mation is available, however. According to the U.S. Department of Agriculture, farmers who plant herbicidetolerant crops do not necessarily use fewer sprays, but they do apply a more benign mix of chemicals. For instance, those who grow herbicide-tolerant soybeans typically avoid the most noxious we

16、ed killer, turning instead to glyphosate herbicides (苷磷除草剂), which are less to toxic and degrade more quickly.Insect-resistant crops also bring mixed benefits. To date. insect resistance has been provided by a gene from the soil bacterium Bacillus thuringiensis (Bt) (杆菌苏立菌) This gene directs cells t

17、o manufacture a Crystalline protein that is toxic to certain insects-especially caterpillars and beetles that gnaw on crops-but does not harm other organisms. The toxin gene m different strains of B. thuringiensis can affect different mixes of insects, so seed makers can select the version that seem

18、s best suited to a particular crop. Of all the crops carrying Bt genes, cotton has brought the biggest drop in pesticide use. According to the Environmental Protection Agency, in 1999 growers in states using high amounts of Bt cotton sprayed 21 percent less insecticide than usual on the crop. Thats

19、a “dramatic and impressive“ reduction, says Stephen Johnson, an administrator in the EPAs Office of Pesticide Programs. Typically, Johnson says, a farmer might spray insecticides on a cotton field 7 to 14 times during a single growing season. “If you choose a Bt cotton product, you may have little o

20、r no use for these pretty harsh chemicals,“ he notes. Growers of Bt com and potatoes report less of a pesticide reduction, partly because those plants normally require fewer pesticides and face fluctuating numbers of pests.Defining the environmental risks of GM crops seems even harder than calculati

21、ng their benefits. At the moment, public attention is most trained on Bt crops, thanks to several negative studies. Regulators, too, are surveying the risks intensely. This spring or summer the EPA is expected to issue major new guidelines for Bt crops, ordering seed producers to show more thoroughl

22、y that the crops can be planted safely and monitored in farm fields.B At What Cost to Wildlife?/BIn 1998 a Swiss study provoked widespread worry that Bt plants can inadvertently harm unlucky creatures. In this laboratory experiment, green lacewing(草蛉) caterpillars proved more likely to die after eat

23、ing European corn-borer caterpillars that had fed on Bt com instead of regular corn. The flames of fear erupted again a year later, when Cornell University entomologist John Losey and his colleagues reported that riley had fed milkweed (乳草属植物) leaves dusted with Bt corn pollen to monarch butterfly l

24、arvae in the lab and that those larvae, too, had died.“That was the straw that broke the camels back.“ says David Pimentel, also an entomologist at Cornell. Suddenly, all eyes turned to the organisms munching GM plant leaves, nipping modified pollen or wriggling around in the soil below the plants-o

25、rganisms that play vital roles in sustaining plant populations. Another alarming study relating to monarch but-terries appeared last August.But the lab bench is not a farm field, and many scientists question the usefulness of these early experiments. The lab insects, they note, consumed far higher d

26、oses of Bt toxin than they would outside, in the real world. So researchers have headed into nature themselves, measuring the toxin in pollen from plots of GM com, estimating how much of it drifts onto plants such as milkweed and, finally, determining the exposure of butterfly and moth larvae to the

27、 protein. Much of that work, done during the 2000 growing season, is slated to be reported to the EPA shortly.According to the agency, however, preliminary studies evaluating the two most common Bt corn plants (from Novartis and Monsanto) already indicate that monarch larvae encounter Bt corn pollen

28、 on milkweed plants but at levels too low to be toxic. What is toxic? The EPA estimates that the insects face no observable harm when consuming milkweed leaves laden with up to 150 corn pollen grains per square centimeter of leaf surface. Recent studies of milkweed plants in and around the cornfield

29、s of Maryland, Nebraska and Ontario report far lower levels of Bt pollen, ranging from just 6 to 78 grains of Bt corn pollen per square centimeter of milkweed leaf surface. “The weight of the evidence suggests Bt corn pollen in the field does not pose a hazard to monarch larvae,“ concludes EPA scien

30、tist Zigfridas Vaituzis, who heads the agencys team studying the ecological effects of Bt crops.But the jury is still out. “Theres not much evidence to weigh.“ notes Jane Rissler of the Union of Concerned Scientists. “This issue of nontarget effects is just a black hole. and EPA has very little good

31、 data at this point to conclude whether the monarch butterfly problem is real, particularly in the long term.“In an EPA meeting on GM crops last fall. Vaituzis acknowledged the lack of long-term data on Bt crops and insect populations. Such studies “require more time than has been available since th

32、e registration of Bt crops,“ Vaituzis remarked. The EPA, he added, continues to collect Bt crop data but so far without evidence of “unreasonable adverse effects“ on insects in the field.（分数：70.00）(1).Many experts who favor genetically modified foods believe that genetic engineering can help to meet

33、 the demands of the worlds increasing population.（分数：7.00）填空项 1:_(2).Some European countries are restricting the planting and importation of GM agricultural products because GM crops could pose unique risks to the environment and to health.（分数：7.00）填空项 1:_(3).Rice is one of the major GM crops contai

34、ning genes which help to either resist insect or tolerate weed - killing herbicides.（分数：7.00）填空项 1:_(4).Study done in Swiss and Cornell University indicated that Bt crops could have unreasonable adverse effects on insects in the field.（分数：7.00）填空项 1:_(5).To certain extent, GM crops are regarded as _

35、 since the gene inserted into a plant cannot be seen, tasted or touched.（分数：7.00）填空项 1:_(6).The two factors contributing to the appealing of GM crops to farmers are and _ .（分数：7.00）填空项 1:_(7).The plants would be insect resistant as a gene from the soil bacterium could direct cells to produce _ that

36、is toxic to certain insects.（分数：7.00）填空项 1:_(8).Among all the GM crops, Bt genes have proved most effective in _ when the largest reduction in pesticide use has been reported.（分数：7.00）填空项 1:_(9).It is much more difficult to _ than to calculate the benefits of the GM crops.（分数：7.00）填空项 1:_(10).Resear

37、ches in the wild field evaluating the two most common Bt corn plants showed that the toxin absorbed was too _ .（分数：7.00）填空项 1:_三、BPart Listenin(总题数：1，分数：56.00)BQuestions 11to 18 are based on the conversation you have just heard./B（分数：56.00）A.The man should try to be more understanding.B.The mans wif

38、e should be more understanding.C.The mans negative attitude may be derived from his childhood.D.The pessimism of mans wife may be the result of her past experiences.A.A snowstorm.B.An earthquake.C.A traffic accident.D.A hurricane.A.The two speakers are classmates.B.The man is majoring in elementary

39、education.C.The woman is majoring in elementary education.D.The two speakers got to know each other in a class.A.Shes got a stomachache.B.She feels perfectly fine.C.Shes going to get married.D.Shes going to have a baby.A.It is the best city hes ever visited.B.It was worse than he had expected.C.It i

40、s difficult to get around in the city.D.The hotel service is terrible in the city.A.To encourage them.B.To stop them immediately.C.To give some explanation.D.To leave them alone.A.Unemployment.B.Family breakup.C.Mental problems.D.Drinking.A.The woman is the mans boss.B.The man is the womans husband.

41、C.The woman is the headmaster of a school.D.The woman wants to know something about a student.四、BQuestions 19 to(总题数：1，分数：21.00)A.A businessman in a store.B.A wander in the street.C.Amateur detective.D.A man with plain clothes.A.Fifteen cigarette fighters.B.Fifty cigarette lighters.C.Sixty lipsticks

42、.D.An identity card.A.At last, the man gave a break to the woman.B.The woman was arrested by the man.C.The man gave choices to the woman.D.The man missed the woman.五、BQuestions 22 to(总题数：1，分数：28.00)A.Eggs.B.Diets.C.Protein.D.Exercises.A.One; Two; OneB.Two; One; One.C.One; One; Two.D.Two; One;Two.A.B

43、ecause she believed eggs were not very expensive and also contained a lot of protein.B.Because she thought her heart was strong and eating too much protein could not hurt her heart.C.Because she had been told that eating eggs could help her to have a fine figure.D.Because she liked eggs so much that

44、 she could not stand if she didnt cat eggs every day.A.One week.B.One month.C.Two days.D.Three days.六、BSection B/B(总题数：1，分数：21.00)BPassage One Questions 26 to 28 are based on the passage you have just heard./B（分数：21.00）A.Probing into the privacy of famous people.B.Short articles about less important

45、 events.C.Colorful pictures and smaller size.D.All above.A.The Daily Star.B.The Times.C.The Daily Telegraph.D.The Daily Minor.A.The Independent.B.The Financial Times.C.The Daily Mirror.D.The Daily Telegraph.七、BPassage Two(总题数：1，分数：21.00)A.Life was easy and food was easy to find.B.People care more ab

46、out how to survive.C.The people took care of each other out of love.D.There are many developed individual monetary systems.A.This need to use the services of people who were not physically near.B.This need to have a common set of values.C.The fear of things that were more different than what people

47、were used to.D.This need to store wealth.A.How the survival skills of the early people influenced their diets.B.This need to learn how to save money;C.The increasingly complex relationship between values and the use of money.D.The difficulty of trading larger and larger amounts of good.八、BPassage Th

48、ree(总题数：1，分数：28.00)A.Neither of the two types of rockets is very economical.B.The liquid-fuel rocket is best.C.Each type of rocket has certain advantages.D.The solid-fuel rocket is best.A.The rocket should be inexpensive to construct.B.The rocket is capable of lifting heavy spacecraft into orbit.C.The rocket should be easily controlled.D.The rocket should be inexpensive to operate.A.Because of its size.B.Because of its fuel.C.Because of its complicated engine.D.Because of its burning time.