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can have done

can have done 通常只用于否定句和疑问句。用于否定句时表否定推断，推测肯定没做；用于疑问句时意为“难道真的做了吗”，表示怀疑。例如：

Can he have done such a foolish thing? (= Is it possible …?)
他会做这样的傻事吗？（表怀疑）

He can't have taken it home.
他不可能把它带回家了。（表不可能）

could have done

could have done 可用于肯定句、疑问句和否定句。用于肯定句既可以表示过去能够做而实际未做，有惋惜、遗憾或委婉批评之意，也可以表示对过去动作的推测；用于否定句和疑问句的情况与can have done相同。例如：

You could have done better, but you didn't try your best.
你本可以做得更好，但是你没有尽力而为。（表惋惜）

This glass is cracked. Someone could have dropped it.
这个玻璃杯破了。可能是谁把它掉在地上了。（表推测过去）

Could he have left the work unfinished?
他会丢下工作不干了？（表怀疑）

He couldn't have checked out so early.
他不可能这么早就离开了。（表不可能）

注意：can't have done 的语气比 couldn't have done 要强一些。例如：

He can't have been to that town.
他根本不可能去过那座城市。（语气略强）

The measurement couldn't have been wrong.
测量不可能出错了吧。（语气稍弱）

学海导航讲解

learning about first aid is the best way to make sure that we will not have to feel that we could have done more.

学习急救时保证遇到此类事情不留遗憾的最佳途径。

could have done 的用法

1. 用于肯定句，否定句和疑问句中，对过去的动作进行可能性的推测，也可用can have done. 用于肯定句中相当于may/might have done. 例如：

 he can /could have left earlier.( can/could have left 相当于may/might have left)

surely she can /could mot have arrived so early.

can/could he have left already?

2.用于肯定句中表示过去本来能够做某事而未做。

you could have caught the early train.(事实上没搭上)

考与练习

1.————————————————————————————————（那会是舒适的旅行吗）since there were 6 people in the little car?

1.Can that have been a comfortable journey 个人意见 ： 可用Can也可用could

2.I____________________(本可以更加用功些的)，but as a matter of fact,I have wasted too much time.

 can have studied harder 个人意见: 应将Can改为could

2011高考课程全国卷 They ____have arrived at lunchtime but their flight was delayed.

A. will B.can C. must D. should 解析D  他们本应该午餐时间到达，可是他们的飞机晚点了。本题考查情态动词的用法。 Can用在疑问句中和否定句中表推测，可能

2014年成都一诊

7. In his teens, Charles Dickens lived a poor life, which  B___have contributed to his later writing.

A.can  B.must  C.should  D.need

can have done 通常只用于否定句和疑问句。用于否定句时表否定推断，推测肯定没做

can have done用法小结