练习题：

　　1. The prevention and treatment of AIDS is _____________________________ .

　　2. Because of the leg injury, the athlete ___________________________ .

　　参考答案：

　　1. The prevention and treatment of AIDS is the field we can cooperate/ the field in which we can cooperate

　　本题考查对定语从句的掌握。领域是the field，我们可以合作的作the field的定语从句，引导词可以用where/which，where可以省略，which后须加in。

　　2. Because of the leg injury, the athlete decided to quit the match

　　本句话是在陈述一件已经发生的事情，应用一般过去时态，因此用decided，退出比赛用quit the match来表示。