托福-4 (1)及答案解析.doc
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1、托福-4 (1)及答案解析(总分:120.66,做题时间:90 分钟)一、BREADING/B(总题数:7,分数:35.50)READING SECTION DIRECTIONSThe Reading section measures your ability to read and understand passages in English. You will read five passages and answer questions about them. Answer all questions based on what is stated or implied in the p
2、assages. Most questions are worth one point. The last question in each set is worth more than one point. For this question, the directions will indicate how many points you can receive. Some passages have one or more words in bold type. For these bolded words, you will see a definition in a glossary
3、 at the end of the passage. Allow 20 minutes to read each passage and answer the questions about it. You may now begin the first passage. BSet 1/BNORTH AMERICAN GRASSLANDS1 In North America, native grasslands occur primarily in the Great Plains in the middle of the continent. The North American prai
4、rie biome is one of the most extensive grasslands in the world, extending from the edge of the Rocky Mountains in the west to the deciduous forest in the east, and from northern Mexico in the south to Canada in the north. Average annual rainfall ranges from about 40 cm (16 inches) in the west to 80
5、cm (31 inches) in the east. Average annual temperatures range between 10 degrees and 20 degrees Celsius (50 to 68 degrees Fahrenheit). In the moist regions of the North American grasslands, especially in the northern Great Plains, rainfall is distinctly seasonal, and temperatures can vary widely fro
6、m very hot in summer to bitter cold in winter. 2 One hundred years ago, the Great Plains grasslands were one vast, unbroken prairie. Much of the prairie is now farmland, the most productive agricultural region in the world, dominated by Bmonocultures/B of cereal grains. Wheat, barley, soybeans, corn
7、, and sunflowers occupy the land that was once prairie. In areas given over to grazing lands for cattle and sheep, virtually all the major native grasses have been replaced by Ualien/U species. 3 An important feature of the northern Great Plains grasslands is the presence of millions of glacial depr
8、essions that are now small ponds known as prairie potholes. They were formed during the most recent Ice Age, when streams flowed in tunnels beneath glacially formed sandy ridges. When the Ice Age ended around 12,000 years ago, the retreating glaciers created about 25 million depressions across a 300
9、,000-square-mile landscapeabout 83 potholes per square mile. As the ice blocks melted, much of the water was left behind, forming wetlands ranging in size from a tenth of an acre to several acres. The wetlands were soon surrounded by fluttering waves of grasses: shortgrass, mixed grass, and tallgras
10、s. 4 UToday these small wetlands still cover the prairies, although much of the landscape including both native grasses and potholeshas been transformed to cropland and grassland for grazing./U What does remain of the wetlands, however, still serves as an important breeding area for more than 300 bi
11、rd species, including large numbers of migrating shorebirds and waterfowl. The potholes fill up with water during spring rains and usually dry out by late summer. Every spring, birds arrive in great numbersnorthern pintails, mallards, coots, and pied-billed grebes4 to 6 million strong, to mate in th
12、e seasonal wetlands that dot portions of Minnesota, Iowa, North and South Dakota, Montana, Alberta, Saskatchewan, and Manitoba. Prairie pothole country produces half of North Americas 35 to 40 million ducks and is renowned worldwide as a “Uduck factory/U.“ 5 Recently biologists have discovered that
13、the prairie pothole region is potentially a vast carbon sink: a natural sponge that absorbs carbon dioxide emissions from cars, factories, and power plants. Carbon dioxide is the most common of all the pollutants acting as greenhouse gases that heat up the atmosphere. Fortunately, however, carbon di
14、oxide is captured naturally and stored in trees, soil, and plants. Scientists have termed Uthis/U “carbon sequestration.“ They have determined that prairie potholes hold an average of 2.5 tons of carbon per acre per year when not being farmed. This means that if the entire pothole region in the Unit
15、ed States and Canada were to stop being farmed, the region would store about 400 million tons of carbon over 10 yearsthe equivalent of taking almost 4 million cars off the road. Thus, preserving the potholes could be a way to Uoffset/U greenhouse gas emissions that are warming the planet. Glossary:
16、biome: one of the worlds major natural communities, classified by predominant vegetation monoculture: cultivation of large land areas with a single plant variety (分数:7.02)(1).All of the following statements are true of the northern Great Plains EXCEPT(分数:0.54)A.Summer temperatures are very hot, whil
17、e winter temperatures are very cold.B.An unbroken prairie now extends from the western mountains to the eastern forest.C.The original vegetation consisted of shortgrass, mixed grass, and tallgrass.D.A large number of small wetlands are found throughout the region.(2).What has taken place in the Grea
18、t Plains grasslands during the last century?(分数:0.54)A.The average annual rainfall has risen and fallen several times.B.Large parts of the prairie have been converted to agricultural use.C.Melting glaciers have formed numerous depressions in the soil.D.Scientists have transformed the region into one
19、 large carbon sink.(3).The word Ualien/U in paragraph 2 is closest in meaning to(分数:0.54)A.healthyB.simpleC.cheaperD.imported(4).The prairie potholes owe their origins mainly to(分数:0.54)A.the variation in temperature throughout the yearB.the glaciers that melted at the end of the last Ice AgeC.the h
20、eavy rains that fall in the spring and summerD.the increase in greenhouse gases in the atmosphere(5).Which sentence below best expresses the essential information in the highlighted sentence in paragraph 4? Incorrect choices change the meaning in important ways or leave out essential information.(分数
21、:0.54)A.The wetlands completely cover the landscape, making it difficult to grow crops and grass for grazing.B.The native grasses that grew in the potholes have been replaced with crops that are more beneficial.C.Except for the potholes region, the entire prairie has been converted to cropland and g
22、razing land.D.Even though a large portion of the prairies is used for crops and grazing, the small ponds remain.(6).The word Udot/U in paragraph 4 is closest in meaning to(分数:0.54)A.coverB.drainC.warmD.damage(7).Why does the author use the term “Uduck factory/U“ in paragraph 4?(分数:0.54)A.To point ou
23、t that ducks are the regions main product for exportB.To emphasize the areas value as a breeding ground for ducksC.To illustrate the tremendous growth of the poultry industryD.To show that the potholes are important to the regions economy(8).What is the function of a carbon sink?(分数:0.54)A.It regula
24、tes carbon emissions from human activities.B.It measures the amount of carbon dioxide in the ecosystem.C.It collects and drains seasonal rainwater from the soil.D.It removes carbon dioxide naturally from the atmosphere.(9).The word Uthis/U in paragraph 5 refers to(分数:0.54)A.the emission of carbon di
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- 托福 41 答案 解析 DOC
