托福-52及答案解析.doc
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1、托福-52 及答案解析(总分:120.00,做题时间:90 分钟)一、READING(总题数:0,分数:0.00)二、Set 1(总题数:1,分数:14.00)THE ATLANTIC EEL1 The mysterious qualities of eels have captivated many scientists. In 1886, a French zoologist put a tiny leaf-shaped saltwater fish into a tank in his laboratory. The fish, about four centimeters long,
2、startled the scientist when it turned into a tiny eellong, rounded, and clear as window glass. Ten years later, another zoologist observed the same metamorphosis in the Mediterranean Sea and concluded that salt water was important to the process. In 1920, Danish biologist Johannes Schmidt tracked ee
3、ls in the Atlantic Ocean, eventually finding individuals of the smallest size in the Sargasso Sea, an area of the North Atlantic between the West Indies and the Azores that is approximately 1,100 kilometers wide and 3,200 kilometers long and surrounded by four major ocean currents. 2 Atlantic eels h
4、ave five life phases: larva, glass eel, elver, immature yellow eel, and mature silver eel. Eels are catadromous fish, living most of their lives in fresh water and then migrating to the sea to reproduce. Their migration is an epic life journey, north through the Atlantic, toward the shore, into rive
5、rs and lakes, and eventually back to the Sargasso Sea, swimming in the open water by night. Scientists have not yet fully documented adult eels arriving at the Sargasso, or eels mating or laying eggs there, but they have observed the newly hatched larvae clustering in the floating Sargassum weed. Th
6、e tiny larvae rise to the surface, where they begin their journey by drifting on the Gulf Stream toward either North America or Europe. A year may pass before the young fish swim toward the shore and fresh water. As they approach the coast, the larvae transform into transparent glass eels, five to s
7、even centimeters in length. It is not yet known how the eels find their way inland, but once glass eels leave the ocean and enter fresh water, they swim upstream, eventually turning into thin, black, ten-centimeter elvers. 3 As the elvers grow, they change into adolescent yellow eels, long and slend
8、er with brownish-yellow sides and bellies. Yellow eels spend the next several years in flesh water, living in rivers and lakes for up to twenty years. Nearly all of the eels in lakes are female, while those in rivers and estuaries are mainly male. As the adolescents mature into adults, their eyes gr
9、ow larger, their backs darken, their sides become silver, and their bellies turn silver-white. They start changing into mature silver eels, ready to begin their southward migration to the Sargasso Sea in late autumn. The transformation into sexually mature fish occurs deep in the Atlantic, during th
10、e long swim back to their mating site. 4 During their long migration, eels face numerous hurdles. Most of these are the result of human activity, such as the dams, weirs, and other physical impediments that have compromised many river systems. Young black elvers require help getting past dams as the
11、y migrate upstream. Because eels are able to breathe through their skin as well as their gills, they can travel over wet surfaces on land, so in some locations biologists have devised wet ramps to assist their climb. During their downstream journey, silver eels can be killed when they swim into the
12、turbines of hydroelectric dams, and a river“s entire eel run can be destroyed in just a few nights. To combat the problem, some energy companies slow the rotation of the blades during the migration so that the eels might pass safely through the turbines. Another hurdle to the eels“ passage is the pr
13、esence of ancient eel weirs, structures of various types built by every human culture that ever inhabited the region. Natural predators also take a toll: eagles, osprey, snapping turtles, and bass all feed on eels. 5 Overfishing and exploitive fisheries have caused eel populations to plummet. Fisher
14、ies target eels at three phases of their lives. Before the tiny glass eels can reach shore, thousands are trapped in nets for export to fish farms in Asia. Yellow eels are caught in eel pots for bait, and silver eels are caught in traps for specialty markets around the world. In addition to overfish
15、ing, eels will face a more serious threat if climate change alters the speed or direction of the currents around the Sargasso Sea. Even a slight shift in the currents would impact the mating and hatching territories of the Atlantic eel.(分数:14.00)(1).The word metamorphosis in paragraph 1 is closest i
16、n meaning to(分数:1.00)A.type of movementB.change in appearanceC.swimming abilityD.reduction in size(2).What is the main purpose of paragraph 1?(分数:1.00)A.To introduce the phenomenon of the eel“s life phasesB.To contrast the discoveries of three scientistsC.To entertain readers with scientific mysteri
17、esD.To emphasize the eel“s need for both salt and fresh water(3).According to the passage, one characteristic that defines catadromous fish is(分数:1.00)A.their ability to navigate by smellB.their very long life spanC.their preference for a diet of Sargassum weedD.their migration from fresh water to s
18、alt water(4).Scientists have direct evidence of which eel behavior in the Sargasso Sea?(分数:1.00)A.Larvae swimming among the plantsB.Glass eels transforming into elversC.Adolescents becoming adultsD.Adult females dying after laying eggs(5).The word drifting in paragraph 2 is closest in meaning to(分数:
19、1.00)A.feedingB.strugglingC.hatchingD.riding(6).According to paragraph 2, there is scientific uncertainty about(分数:1.00)A.where the eels go to reproduceB.what the newly hatched eels eatC.how the eels locate fresh waterD.when the eels become black in color(7).One difference between eels living in riv
20、ers and those living in lakes is(分数:1.00)A.the color of their backs, sides, and belliesB.the level of competition with other speciesC.the season in which their migration beginsD.the relative numbers of females and males(8).Which sentence best expresses the essential information in the highlighted se
21、ntence in paragraph 4? Incorrect choices change the meaning in important ways or leave out essential information.(分数:1.00)A.Dams and weirs have improved river systems for humans and eels.B.Human activity has created hurdles that block the eels“ river passage.C.Eels had few physical problems until hu
22、mans changed the course of rivers.D.The effects of human activity have been both positive and negative.(9).The word combat in paragraph 4 is closest in meaning to(分数:1.00)A.documentB.studyC.reduceD.ignore(10).Paragraph 4 supports which of the following statements about eel migration?(分数:1.00)A.More
23、eels die in the river part of their migration than in the ocean.B.Sometimes humans can help eels get past impediments in rivers.C.The original purpose of weirs was to assist eels in their migration.D.Natural predators pose the most serious threat to migrating eels.(11).The word plummet in paragraph
24、5 is closest in meaning to(分数:1.00)A.declineB.migrateC.evolveD.disappear(12).It can be inferred from paragraph 5 that the author most likely believes which of the following statements about Atlantic eels?(分数:1.00)A.A net is the most effective type of equipment for capturing eels.B.People are just be
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- 托福 52 答案 解析 DOC