have+been是现在完成时,have been 已经;
所以用现在完成时,结构是have+过去分词(done)had+done是过去完成时,表示在过去这个时间点以前什么事情已经完成了;
例如:
I had done my homework before I went bed yesterday.
扩展资料
We took it as read that he must have been a KGB agent
我们完全相信他曾经是一名克格勃特工。
There have been some problems but basically it's a good system.
虽然出现过一些问题,但这基本上仍不失为一个好系统。
His family have been a very positive influence on him.
他的家庭对他有十分良好的影响。
There have been many changes in recent years.
近几年发生了许多变化。