were的原形是什么,were doing是什么时态？

过去进行时 were、was 是 be 动词的过去时，后加了doing 成为过去进行时were的原形是什么。

（原形：am、is、 are 对应过去时：was、was、were） 定义：过去进行时，是表示过去某个具体时刻正在进行的事情或动作。例句：

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。