新概念英语第一册语法总结(七)
7. 过去进行时
表示过去正在进行的动作，经常用在when, while, as引导的状语从句中。
结构：was/were+doing
When my husband was going into the dining room this morning, he dropped some coins on the floor.
While we were having dinner, my father was watching TV.
