mustn't have done和can't have done的区别最好有例子

mustn't have done和can't have done的区别最好有例子

1. 情态动词must+have done只用于肯定句中，表示对过去发生的事情或状态进行肯定的推测，意为”过去一定做过某事”.

如：

1)It must have rained last night，for the road is all wet.

昨天晚上一定是下雨了，因为路还湿着.
2. 情态动词can/could可用于否定句中，即can't have done/couldn't have done，表示对过去发生的事情或状态的肯定的推测，意为“过去不可能做过，肯定没做过”，与musthavedone正好相反.

如：

1)He can't have taken it home.

他不可能把它带回家.

一般来说，没有must not have done的用法

首先have done表示已经做过,这点就不用谈了. can't have done 表示以前不可能做某事. 例句 ---Where____Margaret have put the empty bottles? ---She________them away.They must be somewhere. A.can;can't have thrown B.must;must have thrown. C.must;needn't D.can;must throw 答案为A.第一个句子是一个疑问句而且表示可能性的推测,所以只能用情态动词can或could,第二句的答语表示对过去的推测,所以用can't have done. 请看常见的“情态动词 + have + 过去分词”的用法： 一、“must + have + 过去分词”表示对过去发生的事情或状态进行推测,语气比较坚定,通常只用于肯定句.如： It must have rained last night,for the ground is wet. You must have been mad to speak to the servant. 二、“can / could + have + 过去分词”表示对过去某种情况的怀疑或不确定.can和could一般用于否定句和疑问句,could的语气较can弱.如： I didn't see her at the meeting this morning; she can't / couldn't have spoken at the meeting. He can't have finished the work so soon. 三、“may / might + have + 过去分词”表示对已发生的动作或存在的状态进行不肯定的推测,might的语气比may弱一点.这种结构主要用于肯定句和否定句,疑问句改用can或could.如： They may not have known it beforehand. You might have read about it in the papers. 四、“need + have + 过去分词”表示过去做了不必做或不需要做的事情,或过去做某事纯属多余.如： Need they have done it last week? I needn't have bought so much wine—only five people came. 五、“should / ought to + have + 过去分词”表示过去本该做某事但没做,其否定式表示过去不该做某事但做了,这种句式含有不满或责备之意,ought to的语气比should强一些.如： You ought to / should have studied harder.你本应该更努力学习的.（但没有） He oughtn't to / shouldn't have done that.他本来就不该做那件事.（可是做了） 六、“would ＋ have ＋ 过去分词”表示对过去的某种情况进行猜测,或本来要做某事却因某种原因未做成,通常用来说明某一情况,但不像用should或ought to那样含有责备之意.如： I guess the poet would have been about twenty when she wrote her first poem. Another worker wouldn't have acted like that.

首先have done表示已经做过,这点就不用谈了. can't have done 表示以前不可能做某事. 例句 ---where____margaret have put the empty bottles? ---she________them away.they must be somewhere. a.can;can't have thrown b.must;must have thrown. c.must;needn't d.can;must throw 答案为a.第一个句子是一个疑问句而且表示可能性的推测,所以只能用情态动词can或could,第二句的答语表示对过去的推测,所以用can't have done. 请看常见的“情态动词 + have + 过去分词”的用法： 一、“must + have + 过去分词”表示对过去发生的事情或状态进行推测,语气比较坚定,通常只用于肯定句.如： it must have rained last night,for the ground is wet. you must have been mad to speak to the servant. 二、“can / could + have + 过去分词”表示对过去某种情况的怀疑或不确定.can和could一般用于否定句和疑问句,could的语气较can弱.如： i didn't see her at the meeting this morning; she can't / couldn't have spoken at the meeting. he can't have finished the work so soon.

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