could have/might have /must have/should have都有什么区别
来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/07/05 22:25:29
could have/might have /must have/should have都有什么区别
情态动词+完成时的内容
1. must have done 表示对已经发生的事情的推测,意为“一定,想必”.这种结构一般只用于肯定句,其否定形式是can't (couldn't)have done ,表示“不可能,肯定不会”.例如:
He didn't hear the phone. He must have been asleep.
2. can(could)have done表示对过去的时间内可能发生的事情的猜测,can have done 一般只用于否定句和疑问句.could have done 还可以用于肯定句,常用来表示本来可能完成而实际未完成的动作.例如:
He can't have finished the work so soon.
3may(might)have done 表示对已经发
生的事情的不太肯定的推测,意为“可能已经,或许已经”.例如:
If we had taken the other road , we might have arrived earlier.
4needn”t have done 指实际上做了本来不必要做的事,意为“本来不必”.例如:
There was plenty of time . She needn”t have hurried.
5. should (ought to )have done 指本该做而实际未做的事,意为“本来应该”.其否定式shouldn”t(oughtn”t)have done 则表示某种行为不该发生但却发生了.例如:
You should have started earlier , but you didn”t.
1. must have done 表示对已经发生的事情的推测,意为“一定,想必”.这种结构一般只用于肯定句,其否定形式是can't (couldn't)have done ,表示“不可能,肯定不会”.例如:
He didn't hear the phone. He must have been asleep.
2. can(could)have done表示对过去的时间内可能发生的事情的猜测,can have done 一般只用于否定句和疑问句.could have done 还可以用于肯定句,常用来表示本来可能完成而实际未完成的动作.例如:
He can't have finished the work so soon.
3may(might)have done 表示对已经发
生的事情的不太肯定的推测,意为“可能已经,或许已经”.例如:
If we had taken the other road , we might have arrived earlier.
4needn”t have done 指实际上做了本来不必要做的事,意为“本来不必”.例如:
There was plenty of time . She needn”t have hurried.
5. should (ought to )have done 指本该做而实际未做的事,意为“本来应该”.其否定式shouldn”t(oughtn”t)have done 则表示某种行为不该发生但却发生了.例如:
You should have started earlier , but you didn”t.
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