题目内容：

She was watching TV when I came in.为什么不用was coming?

优质解答

ing表示动作的持续
ed表示动作的完成
She was watching TV when I came in.我进来时她在看电视.
She was watching TV when I was coming in.我被卡在门口时,她在看电视.（持续做进门的动作,被卡住了,哈哈哈~笑过之后请采纳~