英语的过去进行时用来描述过去某个时间正在进行的动作或状态，其构成是“was/were + 现在分词”。例如：

1. He fell asleep when he was reading.

2. They were always quarrelling.

3. What were you doing at four yesterday afternoon？

4. We were watching TV from seven to nine last night.

5. What was she doing at nine o'clock yesterday？

6. While he was waiting for the bus, he was reading a newspaper.

7. At that time she was working in a PLA unit.

在使用过去进行时的时候，通常会有一个表示过去时间的状语，如last night, last Saturday, at seven o'clock, when, while等。这个状语帮助明确动作发生的时间。

需要注意的是，并非所有动词都可以用于过去进行时。通常，表示状态、感受、认识等静态动词和瞬间动词不用于过去进行时，例如：know, like, hate, belong, care, forget等。

此外，过去进行时有时也可以用于表示过去将来时间内的动作，尤其是当这些动作表示过去的计划或意图时，例如：He didn't know whether she was coming.