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might have done（对过去的猜测）可能、究竟、到底（已经）……，也许已经做了某事（语气比较委婉，可能性不如may have done大）；也表示本来应该（能够、可以）做某事而实际上没有做（表示虚拟语气）；
The only dark cloud on the horizon was that they might have to move house.
唯一的忧虑是他们可能要搬家。
It's tempting to speculate about what might have happened.
大家不禁猜测，到底发生了什么事。
The pills might have helped him,
if only he'd taken them regularly.
他当时要是按时服药，也许可以对他有帮助的。
She might have been killed if the neighbours hadn't intervened.
要不是邻居介入，她可能会没命了。
Perhaps your force of argument might have made some difference.
或许是你的雄辩使情况发生了变化。
He might have let something slip in a moment of weakness.
他可能一时大意说漏了嘴。
I thought you might have invited her over.
我以为你可能已经邀请她过来了。
I heard what might have been an explosion
我听见了一声巨响，可能是爆炸声。
What might have happened is neither here nor there.
曾经发生过什么事已经都不重要了。
It tears me apart to think I might have hurt her feelings.
一想到我可能伤害了她的感情，我就感到痛心。
I ventured to suggest that she might have made a mistake.
我小心地提醒说她可能出了差错。
Honestly, you might have told me!
说实话，你事先应该告诉我呀！《牛津高阶英汉双解词典》（表示虚拟语气）
He might have had the decency to apologize.
他其实应该道个歉的。
You might have told me that before!
你之前应该告诉我那件事情！
The report might have been better written
这份报告本来可以写得更好。（表示虚拟语气）
He might have given you more help，even though he was very busy．
他本可以给你更多的帮助，尽管他很忙。（表示虚拟语气）
might have done有时可用于疑问句中，此时might就相当于can/ could。
有时可表示对过去发生事情的庆幸，意为“差点儿……”。如：
Didn’t you see that car nearly hit me?
你没看见那辆车差点撞到我吗？
I might have been killed.
我差一点儿死掉了。
高考真题在线分析：
-Where is my dictionary?I remember I put it here yesterday．
-You________it in the wrong place．(高考试题)
A．must putB．should have put C．might putD．might have put
【解析】答案为D。因为此题放的动作是发生在过去，所以排除A、C，而should have done是“本应该”，故也被排除掉。
He ____________ you more help, even though he was busy.
训练：
A. might have given B. might not give
C. may not have given D. may give
他可能已经帮助你很多了，即使他很忙。选A
Sorry，I’m late．I_________have turned off the alarm clock and gone back to sleep again．(高考试题)
［A］ mightB．should C．canD．will
对不起，我来晚了，我可能当时把闹钟关上，又睡着了。
【解析】答案为A。B表示本应该……；C本来能够做某事，而实际上未做；D，一般将来完成时，排除。只有A表示过去情况的推测，是正确的。如果换成could，也是可以的。
might not have done也许还没做某事，也许根本就没有做某事
The equipment needed to clean up the spill might not have arrived yet
清理漏油所需要的设备可能还没有送到。
I didn't give my name because if I did I thought you might not have come.
我没有留下我的名字，因为如果我这么做的话，我想你可能就不会来了。
The letter might not have been meant for me at all.
这封信也许根本就不是写给我的。
