They have all been put to shame by a boy who, while playing truant, travelled 1600 miles.

来源：百度知道编辑：UC知道时间：2024/05/23 16:54:13

while后面为什么用ing 形式，请解释，谢谢

while they were playing truant
they were省略
根据在时间原因条件状语从句中如果从句主语与主句一致或者为it,并且从句的谓语动词是be那么从句的主语和系动词be可以一起省略
如 when (you are)crossing the street, be careful
if (it is)possible , we will leave tomorrow
when (he was) told the news , he looked calm.

while、when引导从句，省略了主语，所以用ing形式。

因为while句子的主语和主句的主语是一致的这时可以省略主语和系动词完整的是...while they were playing...

they have no idea at all ()为什么用a They___friends since they met in shanghai?A.have made B.have become C.have been D.have had They have done all they could "to help" him.为什么是"to help"? 请问下面一段里的“they have all these trips down the rapids为何义？ They have done all __ stop the sisease from getting around. Those students don't have to be made ___.They are all diligent students they have all been put to shame by a boy who,while playing truant, They were all very tired,but_____of them would stop to have a rest. They are all upset. They have gone forever.