[外语类试卷]大学英语六级模拟试卷172及答案与解析.doc

1、大学英语六级模拟试卷 172及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a composition on the topic Economic Development and Mol- al Decline. You should write at least 150 words and you should base your composition on the outline (given in Chinese) below:

2、1. 近年来我国经济建设取得了很大成就； 2但与此同时，社会风气随着经济的发展也日益下降； 3. 我的观点 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 1-4, mark： Y (for YES) if the

3、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 Directions: In this part, you will have 15 minutes to go over the passage quickly and answer

4、the questions on Answer Sheet 1. For questions 1 4, 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. For questions 5 10, co

5、mplete the sentences with the information given in the passage. GENETICALLY MODIFIED FOODS Are genetically modified crops an environmental dream come- true or a disaster in the making? Scientists are looking for answers. The world seems increasingly divided into those who favor genetically modified

6、(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, they say, genetic engineering which can induce plants to grow in poor soils or to produce more nutritious foods

7、 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 troubling to accept placidly. Taking that view, many European countries are restricting the planting and importa

8、tion 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 reports on the controversy, are served up in the pages that follow. Two years ago in Edinburgh, Scotland eco -

9、vandals stormed a field, crushing canola plants. Last year in Maine, midnight raiders hacked down more than 3,000 experimental poplar trees. And in San Diego, protesters smashed sorghum and sprayed paint over greenhouse walls. This far - flung outrage took aim at genetically modified crops. But the

10、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 crops now on some 109 million acres of farmland worldwide are invisible. You cant see, taste or touch a gene inserted into

11、 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 precisely what worries people. How, exactly, will GM crops affect the environment- and when will we n

12、otice? Advocates of GM, or transgenic, crops say the plants will benefit the environment by requiring fewer toxic pesticides than conventional crops. But critics fear the potential risks and wonder how big the benefits really are. “We have so many questions about these plants,“ remarks Guenther Stot

13、zky, 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 the fields to get the missing information. Some of their recent findings arc reassuring; others s

14、uggest a need for vigilance. Fewer Poisons in the Soil? Every year U. S. growers shower crops with an estimated 971 million pounds of pesticides, mostly to kill insects, weeds and fungi. But pesticide residues linger on crops and the surrounding soil, leaching into groundwater, running into streams

15、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 of toxic pesticides. Today most GM crops mainly soybean, corn, cotton and canola contain genes e

16、nabling 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 herbicidetolerant types survive when exposed to broad - spectrum weed killers, potentially allow

17、ing farmers to forgo more poisonous chemicals that target specific weed species. Farmers like to limit the use of more hazardous pesticides when they can, but GM crops also hold appeal because they simplify operations (reducing the frequency and complexity of pesticide applications) and, in some cas

18、es, 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 information is available, however. According to the U.S. Department of Agriculture, fa

19、rmers 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 weed killer, turning instead to glyphosate herbicides(苷磷除草剂 ) , which are less to

20、xic and degrade more quickly. Insect - resistant crops also bring mixed benefits. To date, insect resistance bas been provided by a gene from the soil bacterium Bacillus thuringiensis (Bt) (杆菌苏立菌 ). This gene directs cells to manufacture a crystalline protein that is toxic to certain insects especia

21、lly caterpillars and beetles that gnaw on crops-but does not harm other organisms. The toxin gene in different strains of B. thuringiensis can affect different mixes of insects, so seed makers can select the version that seems best suited to a particular crop. Of all the crops carrying Bt genes, cot

22、ton 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 a “dramatic and impressive“ reduction, says Stephen Johnson, an administrat

23、or 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 or no use for these pretty harsh chemicals,“ be notes. Growers of Bt corn an

24、d 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 calculating their benefits. At the moment, public attention is most trained on Bt

25、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 thoroughly that the crops can be planted safely and monitored in farm fields. At W

26、hat Cost to Wildlife? In 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 alter eating European com -borer caterpillars that had fed on Bt corn instead of re

27、gular corn. The flames of fear erupted again a year later, when Cornell University entomologist John Losey and his colleagues reported that they had fed milkweed(乳草属植物 ) leaves dusted with Bt corn pollen to monarch butterfly larvae in the lab and that those larvae, too, had died. “That was the straw

28、 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 - organisms that play vital roles in sustaining plant populations. Another

29、alarming study relating to monarch butterflies 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 doses of Bt toxin than they would outside, in the real world. So researc

30、hers have headed into nature themselves, measuring the toxin in pollen from plots of GM coal, estimating how much of it drifts onto plants such as milkweed and, finally, determining the exposure of butterfly and moth larvae to the protein. Much of that work, done during the 2000 growing season, is s

31、lated 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 on milkweed plants but at levels too low to be toxic. What is toxic?

32、 The EPA estimates that the insects face no observable harm when consuming milkweed leaves laden with up to 150 com pollen grains per square centimeter of leaf surface. Recent studies of milkweed plants in and around the cornfields of Maryland, Nebraska and Ontario report far lower levels of Bt poll

33、en, 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 scientist Zigfridas Vaituzis, who heads the agencys team studying the ecolo

34、gical effects of lit 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 data at this point to conclude whether the monarch butterfly problem

35、 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 the registration of Bt crops,“ Vaituzis remarked. The EPA, he added,

36、continues to collect Bt crop data but so far without evidence of “unreasonable adverse effects“ on insects in the field. 2 Many experts who favor genetically modified foods believe that genetic engineering can help to meet the demands of the worlds increasing population. （ A） Y （ B） N （ C） NG 3 Some

37、 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. （ A） Y （ B） N （ C） NG 4 Rice is one. of the major GM crops containing genes which help to either resist insect or tolerate weed - ki

38、lling herbicides. （ A） Y （ B） N （ C） NG 5 Study done in Swiss and Cornell University indicated that Bt crops could have unreasonable adverse effects on insects in the field. （ A） Y （ B） N （ C） NG 6 To certain extent, GM crops are regarded as _since the gene inserted into a plant cannot be seen, tast

39、ed or touched. 7 The plants would be insect resistant as a gene from the soil bacterium could direct cells to produce_that is toxic to certain insects. 8 It is much more difficult to _ than to calculate the benefits of the GM crops. 9 Among all the GM crops, Bt genes have proved most effective in _

40、when the largest 10 reduction in pesticide use has been reported. 11 Researches in the wild field evaluating the two most common Bt corn plants showed that the toxin absorbed was too_. Section A Directions: In this section, you will hear 8 short conversations and 2 long conversations. At the end of

41、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 read the four choices marked A, B, C and D, and decide which is the best answer. （ A） A

42、trip to the downtown of the city. （ B） A forthcoming boat race. （ C） A rise in postage. （ D） An unfortunate accident. （ A） Hell see if they have more paper. （ B） Shes bound to find it somewhere else. （ C） The paper she wants is out of stock. （ D） He cant accept a check. （ A） 7:13 （ B） 7:30 （ C） 8:13

43、 （ D） 8:30 （ A） Shes a good cook. （ B） She lives far away from the woman. （ C） She often takes trips abroad. （ D） She often helps people. （ A） In a paint shop. （ B） At an art museum. （ C） In a swimming pool. （ D） At lumber yard. （ A） She prefers the stadium. （ B） She agrees with the man. （ C） The li

44、ght isnt bright enough. （ D） The dining hall isnt large enough. （ A） She will go away. （ B） She will be sorry. （ C） She wont quit her job. （ D） She wont buy him a present. （ A） Its too late for the man to go to the concert. （ B） The man must wait for two hours to buy a ticket. （ C） People have alrea

45、dy been standing in line for two hours. （ D） The man can buy a standing-room ticket tomorrow. （ A） The man would like to interview her. （ B） The man was absent from class. （ C） The woman would like to promote DME. （ D） The woman would like to praise Dr. Collin. （ A） Its environmentally friendly. （ B

46、） Its more efficient than other alternative fuels. （ C） It doesnt destroy the ozone. （ D） Its not economical to mass-produce. （ A） There would be a test next week. （ B） There would be a psychology class. （ C） The man would feel better soon. （ D） Mike Andrews didnt take notes. （ A） Registering a cour

47、se. （ B） Closing a computer system. （ C） Applying for an ID card. （ D） Having a part-time job. （ A） Because the woman was ignorant of the information. （ B） Because the woman has only worked for a short time. （ C） Because the man did not understand the rules. （ D） Because the man was not sure about t

48、he deadline. （ A） Birth certification. （ B） ID card. （ C） Proof of address. （ D） Work site. （ A） That the man can rely on her instead. （ B） That the man should not bother the director with this. （ C） That the director will help him out. （ D） That the man had better not expect much of the director. S

49、ection 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, B, C and D. （ A） Three to five. （ B） Three to seven. （ C） Five to seven. （ D） Four to six. （ A） The subjects brain waves. （ B） The subjects body movements. （ C） The subjects eye movements. （ D） The subjects slee