过去进行时表示过去某一时刻或某段时间正在进行的动作。
要点讲解
- 结构：was/were + 动词-ing。
- 标志词：at that time, at 8:00 yesterday, at this time yesterday, then, when/while 从句。
- when 与 while 的区别：when 后接短暂性动作或时间点；while 后接延续性动作：While I was reading, he came in. 我读书时他进来了。
- 过去进行时与一般过去时的区别：过去进行时表示"正在做"（背景），一般过去时表示"做了"（事件）：I was watching TV when the phone rang. 我正在看电视，电话响了。
- 两个过去同时进行用 while：While mother was cooking, father was reading. 妈妈做饭时爸爸在读书。
- 过去进行时常用于故事叙述的背景描写。
经典例句
- At eight last night, I was doing my homework.
昨晚8点，我正在做作业。 - They were playing basketball when it began to rain.
开始下雨时他们正在打篮球。 - What were you doing at this time yesterday?
昨天这个时候你在做什么？
易错提醒
- when 从句动词短暂（came, rang），while 从句动词延续（was reading）；短暂动作用一般过去时。