ground. These motions will __10__ soil into the air __11__ it will be blown away.

　　__12__ this reason, a windbreak is best if it has only sixty to eighty percent of the trees and plants needed to make a solid line.

　　An easy rule __13__ is that windbreaks can protect areas up to ten times the height of the tallest trees in it. There should be __14__ two lines in each windbreak. One line should be large trees. The __15__ line, right next to it, can be shorter trees and other plants with leaves. Locally grown trees and plants are best for __16__.

　　Windbreaks not only __17__ land and crops from the wind. They can also provide __18__ products. These include wood for fuel and longer pieces for making fences. You can get more __19__ about windbreaks and other forms of soil __20__ from the group Volunteers in Technical Assistance.

　　1. A．to form　 B．forming

　　C．formed D．form

　　2．A.for B．in

　　C．off D．with

　　3. A．in block B．in lines

　　C．in pieces D．in place

　　4. A．breaking B．stealing

　　C．damaging D．hurting

　　5. A．made B．done

　　C．proved D．shown

　　6. A．high B．low

　　C．lower D．higher

　　7. A．at B．for

　　C．to D．in

　　8．A.that B．when

　　C．where D．why

　　9. A．completely B．slowly

　　C．quickly D．partly

　　10．A.drop B．raise

　　C．stop D．lift

　　11. A．which B．that

　　C．where D．as

　　12. A．To B．For

C．As D．With