[外语类试卷]大学英语四级模拟试卷493及答案与解析.doc

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1、大学英语四级模拟试卷 493及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed 30 minutes to write a composition on the topic: Online Education. You should write at least 120 words following the outline given below in Chinese: 1. 目前网络教育形成热潮 2. 我 认为形成这股热潮的原因是 3. 我对网络教育的评价 Online Education 二、 Pa

2、rt 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, mark： Y (for YES) if the statement agrees with the information given in the passage;

3、 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 To Save Trees, Fighting One Alien Insect with Others Rusty Rhea sighs wistfully as he talks about the beauty and peace of standing amid a grove (小树林 ) o

4、f deep green hemlocks in Appalachia, some of them up to 160 feet ( 50 meters ) tall and more than 500 years old. “This is a very special tree,“ said Rhea, an entomologist for the U.S. Forest Services Forest Health Protection program in Asheville, North Carolina. “I was brought up here, and I dont wa

5、nt to see another species go by the wayside.“ The evergreen trees, a hallmark of southern Appalachias national parks, are under attack by an invasive insect barely visible to the eye but potent enough to fell the giants of the eastern United States old-growth forests. Already the tiny bug from Japan

6、, known as the hemlock woolly adelgid (HWA), has killed upward of 95 percent of the hemlocks in Virginias Shenandoah National Park. Now they are making their way through the half-million-plus-acre (200,000-plas-hectare) Great Smoky Mountains National Park in North Carolina and Tennessee. The hemlock

7、s shade streams, keeping water temperatures just right for brook trout(鲑鱼 ) and other fish. They also house birds such as the black-throated green warbler, solitary vireo, and northern goshawk, all three of which mainly shelter in stands of hemlock trees. Because of the insects broad impact on the e

8、ntire ecosystem of southern Appalachia, HWA stands to cause wider damage than the American chestnut blight(枯萎病 ) of the early 1900s. That fungus from Europe killed off the once dominant chestnut trees from the northeast United States to the southern Appalachian Mountains. In addition, a species rela

9、ted to HWA, the balsam woolly adelgid, has already killed about 90 percent of the mature Fraser fir trees in the Smokies. Acting Quickly HWA arrived in the U.S. Pacific Northwest via nursery plants from Japan in 1924. By 1951 the tiny invader had been found in Virginia. Since then the insect has spr

10、ead to more than 15 U.S. states. The key to killing the HWA is to catch it early and act quickly. Its already well established in the Great Smoky Mountains, where Rhea and others are trying to stem the spread of the bugs. HWA multiply quickly: All of the insects are females that reproduce asexually

11、(无性地 ), laying several hundred eggs a year. When they get to the nymph, or crawler, stage, they are dormant from about June until October, after which they emerge and establish themselves on trees. Winds and birds and other animals spread the crawlers through the forest. HWA crawlers feed on the new

12、 growth of hemlocks by piercing the twigs that hold the branches, sucking the sap, and injecting toxic saliva. The needles mm from a deep green to a grayish green and eventually die, depriving the tree of nutrition from photosynthesis. An infected tree usually dies within five years of initial attac

13、k. Infection is signaled by either a white, cottonlike material that appears along a trees twigs or by the “baldness“ of a trees upper branches. Plans of Attack In the Pacific Northwest the hemlocks seem to be tolerant of the creatures feeding, and in the cold northeast, winters seem to keep them at

14、 bay. But in the warm southeast, with weather approximating that of the insects native Asian homes, they thrive. Chemical sprays such as insecticidal soaps and horticultural oils as well as trunk or soil injections-have helped to kill some of the HWA infestations. But spraying must be repeated every

15、 six months, and injections are expensive and last only two years at most. These methods cant be used conveniently or safely in remote areas or near the streams where hemlocks grow thickly. Long term, the best way to control the pests appears to be releasing other insects that feed exclusively on HW

16、A. Scientists have studied HWA in Japan and China and identified three such species. One of them, the Sasajiscymnus tsugae (St) beetle, was released in areas of Great Smoky Mountains National Park in 2002. Studying what controls a species in its native habitat-including climate, predators, and host

17、resistance-provided clues about which insects to use against HWA, said Kristine Johnson. Based in Gatlinburg, Tennessee, Johnson is a supervisory forester for Great Smoky Mountains National Park. “Biological control is the only long-term hope to save the trees in the backcountry(穷乡僻壤 ),“ she said. “

18、We have 800 square miles (2,100 square kilometers) of contiguous wilderness. We value the native forest, and its entirely worth defending.“ Risky Business Releasing one species of non-native bug to kill another could be risky business, potentially creating another type of infestation. But scientists

19、 first quarantined and studied the HWA-killer insects. They believe the St beetles are the best answer to the HWA problem and that they wont cause side damage. This tiny black female beetle, the size of a poppy seed, is already spreading in the Great Smoky Mountains. But the beetle and other HWA-kil

20、ler insects are seasonal, so it will take several different ones operating year-round to keep HWA in check, Rhea said. He doesnt believe HWA will be completely eradicated (根除 ) but Will instead be kept in balance by the predator insects. “Were trying to insert a balance in a system thats out of bala

21、nce,“ he said. Each St beetle can lay 200 to 300 eggs, said Ernest Bernard, professor of entomology and plant pathology at the University of Tennessee in Knoxville. Bernards laboratory is one of several that are breeding the beetles. “Each beetle eats hundreds of baby adelgids a year,“ he said. And

22、about 120,000 of the beetles have been released in the past couple years in the Smokies, but it is still too early to measure their impact. One good sign, Bernard said, is that some beetle larvae (幼虫 ) have been found in areas where they were not released, indicating that the HWA killers may be repr

23、oducing and spreading. 2 The passage gives a general description of an invasive insect, HWA. （ A） Y （ B） N （ C） NG 3 Hemlock is a hallmark of southern Appalachias national parks. （ A） Y （ B） N （ C） NG 4 The invasive insect, known as the hemlock woolly adelgid (HWA), is from Japan. （ A） Y （ B） N （ C）

24、 NG 5 The key to killing the HWA is to catch it early and act quickly. （ A） Y （ B） N （ C） NG 6 An infected tree usually dies immediately. （ A） Y （ B） N （ C） NG 7 The Hemlock in the U.S. will be saved from HWA soon. （ A） Y （ B） N （ C） NG 8 The long term, best way to control the pests HWA is spraying.

25、 （ A） Y （ B） N （ C） NG 9 Since 11 the HWA has spread to more than _. 10 Releasing one species of non-native bug to kill another could create _. 11 It will take several different insects operating year-round to _. Section A Directions: In this section, you will hear 8 short conversations and 2 long c

26、onversations. 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 read the four choices marked A, B, C and D, and decide which

27、 is the best answer. （ A） The class thought the demonstration was too complex. （ B） Too many students showed up. （ C） The professor didnt show up, （ D） The professor cancelled it. （ A） Because nine is an odd number. （ B） Because the elevator got stuck. （ C） Because the elevator is too old. （ D） Beca

28、use there arc too many people in the elevator. （ A） The rain has stopped. （ B） She wants to soak her clothes. （ C） She is looking for her clothes. （ D） Its mining heavily. （ A） She goes home for lunch. （ B） She spends her time shopping. （ C） She gets interested in what she is reading. （ D） She doesn

29、t wake up in time. （ A） To buy some potatoes. （ B） To pass him some potatoes. （ C） To have some potatoes. （ D） To help him cook some potatoes. （ A） It involved a few lunches. （ B） There were free lunches. （ C） There were three lunches. （ D） There were more than free lunches. （ A） He decided to conti

30、nue his project. （ B） He was unable to get sufficient money. （ C） Lack of land prevented his success. （ D） He was successful with his project. （ A） Painting the room white. （ B） Buying white furniture. （ C） Waiting the man to decide. （ D） Asking Mr. White for advice. （ A） The possible existence of l

31、ife on other planets. （ B） Methods for building powerful new telescopes. （ C） A technical problem that astronomers cant solve. （ D） The discovery of planets orbiting distant stars. （ A） They studied variations in the appearance of the parent stars. （ B） They were able to see the planets with a teles

32、cope. （ C） They compared the parent stars to the Sun. （ D） They sent astronauts on a mission into space. （ A） Their surface features. （ B） Their chemical composition. （ C） Their temperature. （ D） Their age. （ A） A desire to express oneself and display ones wealth. （ B） Individual taste and love for

33、beauty. （ C） Love for beauty and a desire to impress other people. （ D） Individual taste and a desire to express oneself. （ A） They may be homesick and feel insecure. （ B） They are either cold or very sick. （ C） They may try to attract other peoples attention. （ D） They want to protect themselves fr

34、om physical injuries. （ A） Green. （ B） Yellow. （ C） Red. （ D） Grey. （ A） Reporter and fashion designer. （ B） Husband and wife. （ C） Shop assistant and customer. （ D） Teacher and student. Section B Directions: In this section, you will hear 3 short passages. At the end of each passage, you will hear

35、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） In Washington. （ B） In London. （ C） In New York. （ D） In Yorkshire. （ A） Chewing gums. （ B） Earphones. （ C） Magazin

36、es. （ D） Scat belts. （ A） Cocktail. （ B） Gum. （ C） Earphone. （ D） Computer. （ A） The stewardess. （ B） A passenger. （ C） My friend. （ D） The pilot. （ A） Nobody would take care of the city. （ B） There would be no schools. （ C） There would be no protection from crime. （ D） People would be very happy. （

37、 A） Education. （ B） Public security. （ C） Administration, （ D） Transportation. （ A） They want to stay home and do the housework. （ B） They dont have enough money. （ C） They have too much work and not much free time. （ D） They have more freedom than in the past. （ A） Equivalent to a hydrogen bomb. （

38、B） Equivalent to tons of TNT. （ C） Equivalent to tons of hydrogen bombs. （ D） Equivalent to a ton of TNT. （ A） Lightning and thunder. （ B） Warm air and cold air. （ C） A great deal of water vapor and a rapidly rising air current. （ D） A great amount of vapor and electricity. （ A） Nearly 15,000 degree

39、s Fahrenheit. （ B） Nearly 50,000 degrees Fahrenheit. （ C） Nearly 5,000 degrees Fahrenheit, （ D） Nearly 150,000 degrees Fahrenheit. 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

40、. 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 exact words you have

41、 just heard or write down the 36 With more and more young people getting into trouble with the law, racial workers are very busy. They are trying to keep【 B1】 _out of jail and in school. One way to do this is to keep those young people busy with a【 B2】 _activity. In some places, social workers set u

42、p programs to direct【 B3】 _energy from the drawing of graffiti(涂鸦 )to the【 B4】 _arts. In other places, basketball or baseball teams are set up. Sometimes the young people are【 B5】 _into patrol groups. Then, they are given the job of protecting older citizens that they might【 B6】 _have robbed and att

43、acked. Social workers set up these youth programs to meet the needs of a【 B7】 _area. Social workers are highly trained people and are good at solving community problems. They know how to set up【 B8】 _and get things started. However,【 B9】_These voluntary people encourage the young artists, train the

44、sports teams, and oversee the patrol groups. They do other kinds of work as well. 【 B10】 _. Many social service volunteers do not even have a high-school degree. 【 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 th

45、is section, there is a passage with ten blanks. You are 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 corr

46、esponding 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 The comparatively treeless plains of North Africa have suffered a progressive drying up, both 【 S1】 _and man-made, but the region was【 S2】 _so rich in fertile soil th

47、at the district we now know as the Libyan Desert was, in the old days, part of the granary(粮仓 )of the Roman Empire, and the centre of the Sahara【 S3】 _a busy trading population for a long period. That was when there were【 S4】 _. in plenty and the fields were the traditional “fields of the woods“ - c

48、learings in the forest - and therefore always tree【 S5】 _ It is the trees that lift the water and send【 S6】 _into the air so that it may fall as dew or rain further on. Trees reduce the speed of the wind, and provide shelter and shade; the roots【 S7】 _minerals in the soil and these are carried to th

49、e leaves which, when they have fulfilled their function, return to the earth, giving the soil the combination of minerals that plants require. But through the ages Africa has been【 S8】 _. Successive invaders have felled the forest to provide grazing lands for their flocks and herds. With the removal of the essential tree cover, the water【 S9】 _was broken, the earth became feverish and sick, and in