过去进行时的用法是什么？
1、过去进行时表示过去某段时间内持续进行的动作或者事情。常用的时间状语this morning, the whole morning, all day yesterday, from nine to ten last evening, when, while
例如：
(1)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。
(2)What was he researching all day last Sunday? 上周日他一整天都在研究什么?
(3)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。
(4)It was raining when they left the station. 他们离开车站的时候天正在下雨。
(5)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。
2、过去进行时可以表示在过去某个时间点发生的事情。时间点可以用介词短语、副词或从句来表示。如：
What was she doing at nine o'clock yesterday?昨天晚上九点她在做什么? (介词短语表示时间点)
When I saw him he was decorating his room.当我看见他的时候他正在装饰房间。 (when从句表示时间点)
3、在复合句中，如果主要动作和背景动作都是延续的或同时发生的，那么主从句的动词都可用过去进行时。例如：
While he was waiting for the bus, he was reading a newspaper. 他边等车边看报。 (两个动作都是延续的)
He was cleaning his car while I was cooking. 他擦车时我在做饭。(两个动作同时进行)
4、表示在过去即将发生的动作。如：She asked him whether he was coming back for supper.
5、表示过去的反复性或习惯性的动作，常与副词always,constantly,continually,frequently等连用，常常带有说话人的某种感情色彩。如：
His mother was always working like that.他目前总是那样工作。
6、通常不能用于过去进行时的动词主要有：aGREe, be, believe, belong, care, forget, hate, have(拥有), hear, know, like, love, mean, mind, notice, own, remember, seem, suppose, understand, want, wish等。
过去进行时比较
一般过去时表示在过去某个时间发生的动作或存在的状态(强调一次性动作);而过去进行时则表示在过去某一时刻或某段时间正在进行的动作(强调反复的动作)。
Mary wrote a letter to her friend last night.玛丽昨晚给她的朋友写了封信。(写完了)
Mary was writing a letter to her friend last night.玛丽昨晚一直在给她的朋友写信。(不一定写完)
We built a bridge last winter.去年冬天我们修了一座桥。(建成了)
