一、过去进行时的概念

表示过去某一时刻正在进行的动作或过去某一阶段一直进行的动作。

例：I was doing my homework at 9:00 pm last night.

二、过去进行时的构成：

（1）肯定句：主语+was/were+现在分词+其他

例：He was working when I came in.

（2）否定句：主语+was/were+not+现在分词+其他

例：There weren't working when we arrived.

（3）疑问句：Was/were+主语+现在分词+其他？

例：Were they working when you arrived？。