was done和had been done的区别

问题描述:

was done和had been done的区别
今天学习新二第34课.主要讲的被动语态的过去式和过去完成时的被动语态.
前面的比如he has been worried.he was wanted by the police.这些我都能弄懂.
但是后面他这讲他单车这里我没弄明白.
his bicycle had been found这句话.为什么要用过去完成?
如果用his bicycle was been found不就行了吗?
是不是因为找到这辆单车在警官和他说话之前.所以是过去的过去,用过去完成?
请老师详解,别忽悠.

his bicycle had been found这句话.为什么要用过去完成?
因为再过去之前就被发现了.
如果用his bicycle was been found不就行了吗?
这种用法是错误的.只可能是his bicycle has been found为什么是错的呢?那为什么it is beingsent又成立呢?