1．表示过去某一时刻或阶段正在发生的动作。. I was playing chess at 8 yesterday evening.

　　. When I arrived, they were watching TV.

　　. They were doing housework this time last week.

　　2．用于条件状语从句中表示过去将来进行的动作。. She told me to wake him up if she was sleeping.

　　. I asked my friend to warn me about it as long as I was driving too fast.

　　3．过去某时将发生的事。可参考—2（4）. They told me that they were leaving for New York.

　　. He was going out when I arrived.

　　测试精编：

　　1. My brother ________ while he ________ his bicycle and hurt himself.

　　A. fell / was riding B. feel / were riding

　　C. had fallen / rode D. had fallen / was riding

　　2. He ________ his leg as he ________ in a football match.

　　A. broke / played B. was breaking / was playing

　　C. broke / was playing D. was breaking / played

　　3. -Myfather will be here tomorrow. -I thought that he ________ today.

　　A. was corning B. is coming

　　C. will come D. comes

　　4. Jack was going out of the shop when he collided with an old woman who ________ in.

　　A. come B. was coming C. had been coming D. had come

　　5. Michike couldn't come to the telephone when Mr. Smith called her because she ________ in the lab.

　　A. had been working B. has been working

　　C. was working D. worked

　　答案： 1. A 2. C 3. A 4. B 5. C