B
Farmers use different kinds of soil conservation methods to protect their land from damage by farming and the forces of nature. One important form of soil conservation is the use of windbreaks.
Windbreaks are barriers formed by trees and other plants with many leaves. Farmers plant them in lines around their fields. Windbreaks stop the wind from blowing soil away. They also keep the wind from destroying or damaging crops. They are very important for growing grains, such as wheat.
There have been studies done on windbreaks in parts of West Africa. It is found that grain harvests can be 20% higher in fields protected by windbreaks compared to fields without such protection.
However, windbreaks seem to work best when they allow a little wind to pass through. If the wall of trees and plants stops wind completely, then violent air movements will take place close to the ground. These movements will lift soil into the air where it will be blown away. For this reason, a windbreak is best if it has only 60% to 80% of the trees and plants needed to form a solid line.
An easy role to remember is that windbreaks can protect areas up to ten times the height of the tallest trees in the windbreaks. There should be at least two lines in each windbreak. One line should be large trees. The second line, right next to it, can be shorter trees and other plants with leaves. Locally grown trees and plants are best for windbreaks.
Windbreaks can protect land and crops from the wind. They can also provide wood products. These include wood for fuel and longer pieces for making fences.
24. If the wind is stopped completely, what will happen?
25. If the trees in the windbreak are 20 meters high, the area being protected is ___________.
26. We can learn from the text that ____________.
27. The author develops the passage by the following means EXCEPT ____________.
“These movements”指的就是风被“隔风林”完全阻断之后形成的剧烈运动,反而会导致土壤被吹走,所以答案A正确。
事实细节题。根据文章第三段“If the wall of trees and plants stops wind completely, then violent air movements will take place close to the ground. These movements will lift soil into the air where it will be blown away.”可知,隔风林如果完全阻碍了风的运动,反而会产生相反的效果。
对于文中代词的代指内容不清楚。
倍数的表达方法之一就是:A+倍数+the + length/height/width +of +B;如果隔风林的树木高度是20米,那20的十倍就是200,所以答案选B。
事实细节题。根据文章倒数第二段“An easy role to remember is that windbreaks can protect areas up to ten times the height of the tallest trees in the windbreaks”可知,隔风林保护的最大田地面积可以是最高那棵树高度的十倍。
对英语中倍数的表达不理解。
整篇文章都在讲合理建设隔风林对农田的好处,隔风林可以帮助农田更好的产出。故答案C正确。
事实细节题。根据文章第三段“It is found that grain harvests can be 20% higher in fields protected by windbreaks compared to fields without such protection.”可知,与没有建隔风林的农田相比,建有隔风林的良田产量要高出百分之二十。
D选项忽略了隔风林种的太密对良田的危害。
可以明显看出,对防风林的介绍并不是“遵循时间顺序”来写的,故选项D正确。
全文大意把握题。整篇文章为了介绍防风林的功能,分别使用了作比较,列数据以及举例子等方法。
except的含义是指“除…以外”。