When I saw him he was decorating his room. 当我看见他的时候他正在装饰房间。 (when从句表示时间点)

　　三、 在复合句中，如果主要动作和背景动作都是延续的或同时发生的，那么主从句的动词都可用过去进行时。例如：

　　While he was waiting for the bus, he was reading a newspaper.他边等车边看报。 (两个动作都是延续的)

　　He was cleaning his car while I was cooking. 他擦车时我在做饭。(两个动作同时进行)

　　四、 通常不能用于过去进行时的动词主要有：agree, be, believe, belong, care, forget, hate, have(拥有), hear, know, like, love, mean, mind, notice, own, remember, seem, suppose, understand, want, wish等。例如：

　　误：I was knowing the answer.

　　正：I knew the answer. 我知道答案。

　　误：I wasn‘t understanding him.

　　正：I didn‘t understand him. 我不明白他的意思。

　　句型：

　　肯定句：主语+was/were+doing+其它

　　否定句：主语+was/were+not+doing+其它

　　一般疑问句及答语：Was/Were+主语+doing+其它

　　特殊疑问句：特殊疑问词+was/were+主语+doing+其它

　　What were they doing just now?

　　他们刚才在干什么?

　　典型例题：

　　1) Mary ___ a dress when she cut her finger.

　　A. made　 B. is making　 C. was making　 D. makes

　　答案C. 割伤手指是已发生的事情，应用过去时。同时，when表时间的同时性，“玛丽在做衣服时”提供事情发生的背景，因此用过去进行时。

　　2) As she ___ the newspaper, Granny ___ asleep.