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  3. In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、

In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、

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问题 In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list (A、B、C、D、E、F、G……) to fit into each of the numbered blank. There are several extra choices, which do not fit in any of the gaps. (10 points)

A. Human population growth add more pressures on land.
B. Different factors play role in land degradation.
C. What is land conversion?
D. The protected areas cannot escape from the destruction.
E. The land conversion processes in stages.
F. The land conversion has a great impact on nature.

    The projections of species loss by deforestation lurk a number of crucial but hard-to-plot variables, among which two are especially weighty, continuing landscape conversion and the growth curve of human population.
    (41)______.
    Landscape conversion can mean many rings: draining wetlands to braid roads and airports, turning tall grass prairies under the plow, fencing savanna and overgrazing it with domestic stock, cutting second-growth forest in Vermont and consigning the land to ski resorts or vacation suburbs, slash-and-burn clearing of Madagasar’s rain forest to grow rice on wet hillsides, industrial logging on Boreno to meet Japanese plywood demands.
    (42)______.
    The ecologist Jon Terborgh and a colleague, Carel P. van Schaik, have described a four-stage process of landscape conversion that they call the land-use cascade. The successive stages are. (1) wildlands, encompassing national floral and faunal communities altered little or not at all by human impact; (2) extensively used areas, such as natural grasslands lightly grazed, savanna kept open for prey animals by infrequent human-set fires, or forests sparsely worked by slash-and-bum farmers at low density; (3) intensively used areas, meaning crop riel&, plantations, village commons, travel corridors, urban and industrial zones; (4) degraded land, formerly useful but now abused beyond value to anybody.
    (43)______.
    Among all forms of landscape conversion, pushing tropical forests from the wildlands category to the intensively used category has the greatest impact on biological diversity. You can see it in the central Amazon, where big tracts of rain forest have been felled and burned, in a largely futile attempt to pasture cattle on sun-hardened clay. By the middle of the next century, if the trend continues, tropical forest will exist virtually nowhere outside of protected areas—that is, national park, wildlife refuges, and other official reserves.
    (44)______.
    Human population growth will make a bad situation worse by putting ever more pressure on all available land. The annual increase is, now 80 million people, with most of that increment coming in less developed countries. According to U.N.’s middle estimate, human population will rise from the present 5.9 billion to 9.4 billion by the year 2050. Anyone interested in the future of biological diversity needs to think about the pressures these people will face, and the pressures they will exert in return.
    (45)______.   
    That direction, necessarily, will be toward ever more desperate exploitation of landscape. Even Noah’s ark only manages to rescue paired animals, not large parcels of habitats. The jeopardy of the ecological fragments that we presently cherish as parks, refuges, and reserves is already severe due to internal and external forces, internal, because insularity itself leads to ecological unraveling; and external, because those areas are still under siege by needy and covetous people. Projected forward into a future of 10.8 billion humans, that jeopardy increases to the point of impossibility.
    We shouldn’t take comfort in assuming that at least the parks and reserves like Yellowstone National Park, will still harbor grizzly bears in the year 2150. Those predator populations, and other species down the cascade, are likely to disappear. "Wildness" will be a word applicable only to urban turmoil. Lions, tigers, and bears will exist in zoos. Nature won’t come to an end, but it will look very different.
选项
答案F
解析 本段介绍了土地转化的前三个阶段对自然生态的影响，段首句即为主题句，选项F"土地转化对大自然有着巨大影响"与首句意思相符。
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