have to和must用法的疑问 - 柯帕斯英语网

1.She's not answering the doorbell. She must not be at home.

请问must not表推测时，可以缩写为mustn't吗？话句话说，mustn't是不是只能用于表“禁止”，不能用于表推测？

2.No one else could have done it – it had to be Neville.

If Bley was aboard, he had to have heard me.

They have to have seen her rocket burning as she makes her landing approach, coming in ass-backward.

have to表示对过去的推测时，以下三种形式我搞不清楚该怎么用，还请老师讲解下had to、had to have done、have to have done表推测时有什么区别？

1 must 表示推测用作否定句，为美式英语。英式英语用cannot。

2 have to 表示推测不及must 普通。阅读时知道这是推测性语法即可，自己写东西，最好还是用must.

have to do用于站在现在的立场对现在的情况的推测，had to do用于站在过去的立场对过去情况的推测。

have to have done 只能表示站在现在的立场推测过去，此时意义等于 must have done.

had to have done 用于站在过去的立场推测过去的过去的情况，此时不能用have to have done. 也不能用must have done. 但可以用would have done. 例如下句：

If Bley was aboard, he had to have heard me. 正确

If Bley was aboard, he would have heard me. 正确

If Bley was aboard, he have to have heard me. 错误

If Bley was aboard, he must have heard me. 错误

曹荣禄 -

擅长：动词用法,句法问题 | 采纳率 82% | 回答于 2021-02-27 20:21

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其它 2 个回答

千千学堂 - 英语图书编辑 2021-02-27 10:10

擅长：英语

1. must 的否定式表推测，主要见于美国英语中，参见：

https://www.cpsenglish.com/question/48211

2. have to 表推测的用法可参见：

https://www.cpsenglish.com/question/2662

黎反修 - 英语翻译（已退休） 2021-02-27 10:16

擅长：数词用法,存在句,英语考试

1. 在美式英语用must not表推测时，也可以缩写为mustn't 。如： Then he mustn't be at home. 那么他一定不在家。 (《英汉多功能词典》新编升级版p.1109)