I. 第二部分：语言知识及运用（满分25分）
第一节 完形填空(共10小题；每小题1.5分，满分15分)
Trees are useful to man in three very important ways. They provide him with wood and other __21__ ; they give him shade; they help to prevent drought(干旱)and __22__.
Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important.
