用法

一、过去进行时的主要用法是描述一件事发生的背景;一个长动作发生的时候，另一个短动作发生。常用的时间状语this morning, the whole morning, all day yesterday, from nine to ten last evening, when, while

We were watching TV from seven to nine last night.昨天晚上七点到九点的时候我们在看电视。What was he researching all day last Sunday?上周日他一整天都在研究什么?My brother fell while he was riding his bicycle and hurt himself.我哥哥骑自行车的时候从车上摔下来，受伤了。It was raining when they left the station.他们离开车站的时候天正在下雨。When I got to the top of the mountain, the sun was shining.当我到达山顶的时候，阳光灿烂。