例句
a. — The money has disappeared! Who could have taken it?
— John could have; he was here alone yesterday.
b. The situation was bad but it could have been worse.
当时情况很糟糕，但本来还可能更糟糕。
c. You screamed in your sleep last night. You must have had a terrible dream.
你昨晚睡觉时大喊大叫了，你一定是做了噩梦。
d. I can’t find my sunglasses. I may/might have left them at the restaurant yesterday.
e. The package is gone. Someone might have picked it up by mistake.
（2）表示过去应该或能够做某事而实际并没有做
1）should / ought to have done表示过去应该做某事而实际并没有做，含有批评的意思。用于否定句中，则表示过去不应该做某事而实际做了，也含有批评的意思。
例句
a. You should have phoned me last night.
你昨晚应该给我打个电话。
b. — I feel terribly ill today.
我今天感觉很糟糕。
— You shouldn’t have eaten those mushrooms yesterday. Mushrooms don’t agree with you.
你昨天不应该吃那些蘑菇。你不能吃蘑菇。
2）could have done 表示过去本能做某事而实际并没有做，含有惋惜的意思。
例句
a. You could have told me you were getting married.
你本来可以告诉我你要结婚的事嘛。
b. I could have lent you the money. Why didn’t you ask me?
我那时是能够把钱借给你的，你为什么不向我借？
c. Some women______a good salary in a job instead of staying at home,but they decided not to work for the sake of the family.
A.must make
B.should have made
C.would make
D.could have made
正确答案：D。
（3）表示本来不必做某事，但实际上做了
needn’t have done 表示本来不必做某事但实际做了。
例句
a. —We went to the meeting, but it had been cancelled.
—Oh, so you needn’t have gone.
b. The restaurant was nearly empty. We needn’t have booked a table.