问题
阅读理解
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 , for example . These found that grain harvests can be twenty percent 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 motions will take place close to the ground . These motions will lift soil into the air where it will be blown away . For this reason , a windbreaks is best if it has only sixty to eighty percent of the trees and plants needed to make 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 . These 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 . 1.What is the best title for the passage?
A.Windbreaks are barriers . B.Windbreaks can be used to make fences . C.In general , there are two lines in all in every windbreak . D.Windbreaks can protect areas . |
答案
小题1:C
小题2:B
小题3:C
