have been doing 是现在完成进行时,表过去发生的动作一直在进行到现在.
We have reading an interesting book since last week.
have done 是现在完成时,表在过去发生的动作对现有影响.
So far I have been to Beijing twice.
had done 是过去完成时,表过去的过去.
When I got there he hadgone.
我是从事英语的,不明再问啦.