三者的主要区别为动作的完成状语不同:
1.to do强调去做,但还没做,例:
I have something to do tomorrow.
明天我有些事情要去做.
2.to be doing 强调正在做,例:
Everyone seems to be doing it.
每个人似乎都在这样做。
3. to have done强调的是动作为完成时,例:
They ought to have done something and they haven't.
他们事前应该做一些事情而他们却没有。
to do 不定式的一般式
to be done 一般是的被动
to be doing 一般式的进行时
to have done 不定式的完成式
to have been done 不定式完成式的被动