while 引导时间状语从句的时候,一般是这样的,比如:
While John was watching TV, his wife was cooking.
I got home while dad was reading newspaper.
担不全部是.比如:
While he was a young boy, he was always ready to help others.
Will you watch my clothes while I have a swim.
在 while 引导让步从句的时候,不一定用现在进行时:
I like playing football while you like playing basketball.
上面是比较明显的.你有兴趣的话,到下面链接看看吧:
http://baike.baidu.com/view/84572.htm