2013年托福考试阅读材料专题训练7_第2页

Paragraph 7:■ The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. ■The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil. ■This is usually followed by the drying of the soil and accelerated erosion.■

12. Look at the four squares [■] that indicate where the following sentence can be added to the passage.
This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing.
Where would the sentence best fit?

13-14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Many factors have contributed to the great increase in desertification in recent decades.
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Answer Choices
1. Growing human populations and the agricultural demands that come with such growth have upset the ecological balance in some areas and led to the spread of deserts.
2. As periods of severe dryness have become more common, failures of a number of different crops have increased.
3. Excessive numbers of cattle and the need for firewood for fuel have reduced grasses and trees, leaving the land unprotected and vulnerable.
4. Extensive irrigation with poor drainage brings salt to the surface of the soil, a process that reduces water and air absorption.
5. Animal dung enriches the soil by providing nutrients for plant growth.
6. Grasses are generally the dominant type of natural vegetation in semiarid lands.

 
参考答案：
1. ○2
This is a Vocabulary question. The word being tested is threatened. It is highlighted in the passage. To threaten means to speak or act as if you will cause harm to someone or something. The object of the threat is in danger of being hurt, so the correct answer is choice 2, "endangered."

2. ○2
This is a Factual Information question asking for specific information that can be found in paragraph 3. The correct answer is choice 2, reduced water absorption. The paragraph explicitly states that the reduction of vegetation greatly reduces water absorption. Choice 4, reduced water runoff, explicitly contradicts the paragraph, so it is incorrect. The "spaces in the soil" are mentioned in another context: the paragraph does not say that they increase, so choice 3 is incorrect. The paragraph does not mention choice 1.

3. ○1
This is a Vocabulary question. The word being tested is delicate. It is highlighted in the passage. The correct answer is choice 1, "fragile," meaning "easily broken." Delicate has the same meaning as "fragile."

4. ○1
This is a Factual Information question asking for specific information that can be found in paragraph 5. The correct answer is choice 1: border areas have difficulty "adjusting to stresses created by settlement." The paragraph says that "expanding populations," or settlement, subject border areas to "pressures," or stress, that the land may not "be able to respond to." Choice 2 is incorrect because the paragraph does not discuss "fertility" after desertification. Choice 3 is also incorrect because "irrigation" is not mentioned here. The paragraph mentions "increasing populations" but not the difficulty of "attracting populations," so choice 4 is incorrect.

5. ○4
This is a Vocabulary question. The word being tested is progressively. It is highlighted in the passage. The correct answer is choice 4, "increasingly." Progressively as it is used here means "more," and "more" of something means that it is increasing.

6. ○3
This is a Factual Information question asking for specific information that can be found in paragraph 6. The correct answer is choice 3, "removal of the original vegetation." Sentence 4 of this paragraph says that "the raising of most crops necessitates the prior removal of the natural vegetation," an explicit statement of answer choice 3. Choice 1, lack of proper irrigation techniques, is incorrect because the paragraph mentions only "overirrigation" as a cause of desertification. No irrigation "techniques" are discussed. Choices 2 and 4, failure to plant suitable crops and use of animal waste, are not discussed.

7. ○4
his is a Vocabulary question. A phrase is being tested here, and all of the answer choices are phrases. The phrase is "devoid of." It is highlighted in the passage. "Devoid of' means "without," so the correct answer is choice 4, "lacking in." If you lack something that means you are without that thing.

8. ○4
This is a Factual Information question asking for specific information that can be found in paragraph 9. The correct answer is choice 4, "bring salts to the surface." The paragraph says that the final human cause of desertification is salinization resulting from overirrigation. The paragraph goes on to say that the overirrigation causes the water table to rise, bringing salts to the surface. There is no mention of the process "interfering" with or "limiting" irrigation, or of the "amount of air" the soil is required to absorb, so choices 1,2, and 3 are all incorrect.

9. ○3
This is a Negative Factual Information question asking for specific information that can be found in the passage. Choice 3, "insufficient irrigation," is the correct answer. Choice 1, "soil erosion," is explicitly mentioned in paragraph 2 as one of the primary causes of desertification, so it is not the correct answer. Choice 2, "global warning," is mentioned as a cause of desertification in paragraph 4, so it is incorrect. Choice 4, "raising of livestock," is described in paragraph 7 as another cause of desertification, so it is incorrect. The passage includes excessive irrigation as a cause of desertification, but not its opposite, insufficient irrigation, so that is the correct answer.

10. ○1
This is a Sentence Simplification question. As with all of these items, a single sentence in the passage is highlighted:

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.

The correct answer is choice 1. That choice contains all of the essential information in the highlighted sentence and does not change its meaning. The only substantive difference between choice 1 and the tested sentence is the order in which he information is presented. Two clauses in the highlighted sentence, "The great difficulty of reversing the process" and "the numbers of people affected," have simply been reversed; no meaning has been changed, and no information has been removed. Choices 2,3, and 4 are all incorrect because they change the meaning of the highlighted sentence.

11. ○3
This is an Inference question asking for an inference that can be supported by the passage. The correct answer is choice 3; the passage suggests that the author believes "Desertification will continue to increase." The last paragraph of the passage says that slowing or reversing the erosion process will be very difficult, but that it may occur in those areas that are not too affected already if rigorously enforced anti-erosion processes are implemented. Taken together, this suggests that the author is not confident this until happen; therefore, it can be inferred that he thinks erosion will continue. The passage provides no basis for inferring choices 1, 2, or 4.

12. ○2
This is an Insert Text question. You can see the four black squares in paragraph
7 that represent the possible answer choices here:

■The raising of live stock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation. ■The consequences of an excessive number of livestock grazing in an area are the reduction of the vegetation cover and the trampling and pulverization of the soil. ■This is usually followed by the drying of the soil and accelerated erosion. ■
 The sentence provided, "This economic reliance on livestock in certain regions makes large tracts of land susceptible to overgrazing," is best inserted at Square 2. The inserted sentence refers explicitly to relying on "livestock in certain regions." Those regions are the ones described in the sentence preceding square2, which states that raising livestock is "a major economic activity in semiarid lands." The inserted sentence then explains that this reliance "makes large tracts of land susceptible to overgrazing. " The sentence that follows square 2 goes on to say that "The consequences of an excessive number of livestock grazing in an area are. . ." Thus, the inserted sentence contains references to both the sentence before square 2 and the sentence after square 2. This is not true of any of the other possible insert points, so square 2 is correct.

13-14.○1 3 4
This is a Prose Summary question. It is completed correctly below. The correct choices are 1, 3, and 4. Choices 2, 5, and 6 are therefore incorrect.

 
参考译文：
沙漠已经占据了地球表面积约四分之一，而且最近几十年正以惊人的速度扩张。沙漠化是指类似沙漠的环境漫延到原本并非沙漠的区域。据估计，地球表面另外四分之一的地方正面临沙漠化威胁。

沙漠化主要通过以下过程实现：首先自然植被不断减少，随后风力和雨水加速了土壤的腐蚀。有的时候松散的土壤全部被风刮走，留下石质化的表层；其它情况下细小的沙粒可能会被吹走，而正常沙粒大小的砂子不断堆积，从而形成移动的沙丘或者沙脊。

即便是在保留了土壤表层的区域，植被减少也已成为土壤大量吸取地下水的能力下降的典型因素。雨水对松散土壤的冲击会把细小的粘土颗粒冲到土壤空隙中，封闭了土壤并降低土地表层水的渗透率。地表对水的吸收急剧减少，大量水资源流失，因此土壤的腐蚀率也随即增加。地表吸收水分的能力进一步弱化使得土壤越发干燥，导致植被的进一步流失，于是便形成了土壤沙漠化的恶性循环。

在一些地方，沙漠面积的扩大很大程度上归因于干燥的气候条件。在过去的几千年里，不断增加的温室效应使得一些地方干旱问题愈发严重。倘若空气污染带来的温室效应继续恶化，沙漠化进程会在未来数十年内加速实现。

然而，可以肯定的是，大部分地区沙漠化主要都是由于人类活动造成，而非自然条件导致。沙漠边缘的半干旱土地所处的生态平衡环境非常脆弱，环境压力持续增加，而这些半干旱区域适应环境压力的能力极其有限。人口数量的增加使得人们不断向土地施压，依其提供实物和燃料。在湿润的季节里，土地兴许能够应付这些压力。但是在干旱的季节里，在沙漠周边的土地上，存在着这样一个十分普遍的现象：人类对土地施加的压力远远超过了土地自身减压的能力，因此最终形成了沙漠。

导致沙漠化的主要因素有四个：过度种植，过度放牧，过分砍伐，过度灌溉。由于人口密度增加，人们对粮食作物的种植已经扩展到日益干燥的区域进行。这些区域很有可能经常会发生干旱，所以农作物种植失败是很正常的事情。种植大量农作物需要事先移除天然植被，而农作物欠收后又会留下大面积荒地，非常容易被风力和雨水侵蚀。

在半干旱地区，草坪是主要的天然植被，家畜饲养是当地的一项主要经济活动。在一个地区过量饲养家畜会导致植被覆盖面积减少，土地被大量践踏和碾碎。通常，随之而来的就是土地硬化和加速侵蚀。

在很多国家木材是用来做饭和加热的最主要燃料。人口增加带来的压力促使人们大量砍伐木材，导致许多城市和乡村周围大面积树木和灌木减少。同时人们大量使用烘干的动物排泄物作为替代燃料同样对土壤不利，因为这些珍贵的土壤成分调节剂和植物营养资源将不会再回归至土壤当中。

造成土地沙漠化的最后一个主要人为因素在于人类过度灌溉导致土壤的盐碱化。灌溉多余的水渗透到地下水位。假如没有排水系统的存在，那么地下水位上升，把溶解的盐分带到土壤表面。水分蒸发后，盐分留在了表面，形成白色的地壳层，这一地壳层阻止了空气和水接触地底下的土壤。

沙漠化问题异常严重，这是因为有佷广阔的地区和数量庞大的人群都受到了沙漠化的影响，而且要想逆转沙漠化的进程甚至减缓沙漠化的速度都面临着巨大的困难。一旦土壤被侵蚀，需要再经过几百到上千年的时间才会产生新的土壤。那些大量土壤仍保存完好的地方，亟需一个严谨而有力的保护政策和植被覆盖计划来保护现有土地。