must和have to用法比较讲解

（1）must表示“必须”，“应该”。否定式must not(mustn't)表示“不应该”，“不许可”，“不准”,“禁止”等。在回答带有must的问句时，否定式常用need not(needn't)或don't have to 表示“不必”，而不用must not (mustn't)。
The work must be finished as soon as possible.这件工作必须尽快完成。
You mustn't speak like that.你不能那样说话。
—Must I be home before eight o'clock? 8点之前我必须回家吗？
—Yes, you must./No, you needn't./No, you don't have to. 是的，必须回家。/不，不必了。
（2）must表推测，
①一般只用于肯定句中，译成汉语“一定”，“必定”。
There must be some mistakes.肯定有一些错误。
You must be very tired.你一定很累了。
②如果表示对过去事情的推测，就用"must+完成时"。
You must have left your umbrella in the theatre.你一定把雨伞丢在剧院里了。
His car is still here. He must have gone by bus.他的车还在这里，他一定乘公共汽车走了。
③当must表推测之意时，其否定形式常用can not而不用must not。
He can't have been to your home. He doesn't know your address.他不可能到过你家，因为他不知道你的住址。
What can he be doing at this time of night?夜晚都到这个时候了，他究竟在干什么呢?
（3）must表必然性
You must catch cold if you don't put on more clothes.如果你不多穿些衣服，必然感冒。
All men must die.人固有一死。
Truth must be out.真相总会大白。
（4）have to表示“必须”，“不得不”，在这个意义上与must很接近，但must表示的是说话人的主观看法，而have to 表示的却是客观需要。
I have to go now.我得走了。（客观需要）
I must go now.我必须走。（主观看法）
You have to work hard to make a living.为了谋生你就得努力工作。（客观需要）
You must do what I tell you.你必须按照我告诉你的去做。（主观要求）
（5）have to 有更多的时态形式：现在时，过去时，将来时等，而must只有现在时形式。
We had to be there at 8.我们得8点到那里。
I shall have to go to school tomorrow.明天我得去上学了。
（6）have to 不能代替表推测的must，但在虚拟条件句中用had had to+动词原形表示与过去相反的情况。
You must be joking.你一定是在开玩笑。（不能用have to）
If I had had to do the work, I should have done it in a different way.如果我不得不做这项工作，我会以不同的方式去做。（不能用must）
If I had had to run the factory, I would have had it run by able men.如果我得管理那家工厂的话，我就会让能人来管。（不能用must）

Unit4 Grammar

一、根据句意及汉语提示用wh-word+to-infinitive完成句子。

1. I can't decide ____________________________ (选哪一个).

2. She doesn’t know ________________________________(说什么).

3. Please find out ______________________(怎么解决）the problem.

4. Sorry, I forget ________________________________(何时何地开会).

5. Do you know________________________________(向谁征求建议)？

6. Sandy is wondering ________________________________(在哪里求助）.

must和have to用法比较讲解

（1）must表示“必须”，“应该”。否定式must not(mustn't)表示“不应该”，“不许可”，“不准”,“禁止”等。在回答带有must的问句时，否定式常用need not(needn't)或don't have to 表示“不必”，而不用must not (mustn't)。
The work must be finished as soon as possible.这件工作必须尽快完成。
You mustn't speak like that.你不能那样说话。
—Must I be home before eight o'clock? 8点之前我必须回家吗？
—Yes, you must./No, you needn't./No, you don't have to. 是的，必须回家。/不，不必了。
（2）must表推测，
①一般只用于肯定句中，译成汉语“一定”，“必定”。
There must be some mistakes.肯定有一些错误。
You must be very tired.你一定很累了。
②如果表示对过去事情的推测，就用"must+完成时"。
You must have left your umbrella in the theatre.你一定把雨伞丢在剧院里了。
His car is still here. He must have gone by bus.他的车还在这里，他一定乘公共汽车走了。
③当must表推测之意时，其否定形式常用can not而不用must not。
He can't have been to your home. He doesn't know your address.他不可能到过你家，因为他不知道你的住址。
What can he be doing at this time of night?夜晚都到这个时候了，他究竟在干什么呢?
（3）must表必然性
You must catch cold if you don't put on more clothes.如果你不多穿些衣服，必然感冒。
All men must die.人固有一死。
Truth must be out.真相总会大白。
（4）have to表示“必须”，“不得不”，在这个意义上与must很接近，但must表示的是说话人的主观看法，而have to 表示的却是客观需要。
I have to go now.我得走了。（客观需要）
I must go now.我必须走。（主观看法）
You have to work hard to make a living.为了谋生你就得努力工作。（客观需要）
You must do what I tell you.你必须按照我告诉你的去做。（主观要求）
（5）have to 有更多的时态形式：现在时，过去时，将来时等，而must只有现在时形式。
We had to be there at 8.我们得8点到那里。
I shall have to go to school tomorrow.明天我得去上学了。
（6）have to 不能代替表推测的must，但在虚拟条件句中用had had to+动词原形表示与过去相反的情况。
You must be joking.你一定是在开玩笑。（不能用have to）
If I had had to do the work, I should have done it in a different way.如果我不得不做这项工作，我会以不同的方式去做。（不能用must）
If I had had to run the factory, I would have had it run by able men.如果我得管理那家工厂的话，我就会让能人来管。（不能用must）

Unit4 Grammar

一、根据句意及汉语提示用wh-word+to-infinitive完成句子。

1. I can't decide ____________________________ (选哪一个).

2. She doesn’t know ________________________________(说什么).

3. Please find out ______________________(怎么解决）the problem.

4. Sorry, I forget ________________________________(何时何地开会).

5. Do you know________________________________(向谁征求建议)？

6. Sandy is wondering ________________________________(在哪里求助）.