文勇的新托福黄金&ccedil

waterabsorptionisgreatlyreducedconsequentlyrunoffisin

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Unformatted text preview: lex ○Valuable 4. According to paragraph 5, in dry periods, border areas have difficulty ○Adjusting to stresses created by settlement ○Retaining their fertility after desertification ○Providing water for irrigating crops ○Attracting populations in search of food and fuel Paragraph 6: Four specific activities have been identified as major contributors to the desertification processes: overcultivation, overgrazing, firewood gathering, and overirrigation. The cultivation of crops has expanded into progressively drier regions as population densities have grown. These regions are especially likely to have periods of severe dryness, so that crop failures are common. Since the raising of most crops necessitates the prior removal of the natural vegetation, crop failures leave extensive tracts of land devoid of a plant cover and susceptible to wind and water erosion. 5. The word progressively in the passage is closest in meaning to ○Openly ○Impressively ○Objectively ○Increasingly 6. According to paragraph 6, which of the following is often associated with raising crops? ○Lack of proper irrigation techniques ○Failure to plant crops suited to the particular area ○Removal of the original vegetation ○Excessive use of dried animal waste 7. The phrase devoid of in the passage is closest in meaning to ○Consisting of ○Hidden by ○Except for ○Lacking in Paragraph 9: The final major human cause of desertification is soil salinization resulting from over irrigation. Excess water from irrigation sinks down into the water table. If no drainage system exists, the water table rises, bringing dissolved salts to the surface. The water evaporates and the salts are left behind, creating a white crustal layer that prevents air and water from reaching the underlying soil. 8. According to paragraph 9, the ground’s absorption of excess water is a factor in desertification because it can ○Interfere with the irrigation of land ○Limit the evaporation of water 22 Mail@liuwenyong.com 在在在在在在 www.liuwenyong.com 在在在在在在在在在在在在在在在,在在在在在在在在在在 ○Require more absorption of air by the soil ○Bring salts to the surface 9. All of the following are mentioned in the passage as contributing to desertification EXCEPT ○Soil erosion ○Global warming ○Insufficient irrigation ○The raising of livestock Paragraph 10: The extreme seriousness of desertification results from the vast areas of land and the tremendous numbers of people affected, as well as from the great difficulty of reversing or even slowing the process. Once the soil has been removed by erosion, only the passage of centuries or millennia will enable new soil to form. In areas where considerable soil still remains, though, a rigorously enforced program of land protection and cover­crop planting may make it possible to reverse the present deterioration of the surface. 10. Which of the sentences below best expresses the essential information in the highlighted senten...
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