问题描述：
while,when,as 引导时间状语从句,尤其是过去进行时的区别.要简单易懂的,常用的.
问题解答：
我来补答
合并下列句子,如果你会,你在这方面的问题就解决了：
He was getting off the bus.He fell and hurt himself
1 While he was getting off the bus,he fell and hurt himself
2 When he fell and hurt himself,he was getting off the bus
3 He was getting off the bus when he fell and hurt himself
4 He fell and hurt himself while he was getting off the bus.
5 As he got off the bus,he fell and hurt himself
6 He fell and hurt himself as he got off the bus.
简单易懂,没有长篇大论,不过你需要比较和记住.
