在英语学习的过程中，我们会发现很多词汇有着相同的意思，但用法却很不一样。今天老师和大家分享【have to和must】的比较，另外附上易错考点回顾 闯关提分训练。
两词都是'必须'的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。
My brother was very ill, so I had to call the doctor in the middle of the night.
我弟弟病得很厉害，我只得半夜里把医生请来。(客观上需要做这件事)He said that they must work hard.
他说他们必须努力工作。（主观上要做这件事）
have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。
He had to look after his sister yesterday.
他昨天不得不照顾他的姐姐。
在否定结构中：don't have to 表示"不必"；mustn't 表示"禁止"，
You don't have to tell him about it. 你不一定要把此事告诉他。
You mustn't tell him about it.
你一定不要把这件事告诉他。
【易错考点回顾】must和have to
【易错点睛】
1. 表示必须此时可用于肯定句、否定句或疑问句，用于否定句时，mustn’t的意思是“一定不要、不能”。如：You must finish the work tonight. 你必须今晚完成这项工作。Adverbs mustn’t be put between the verb and the object. 副词不能放在动词和宾语之间。
2. 表示推测意为“一定是”，通常只用于肯定句，表示有把握的肯定推测。如：Jane’s light is on. She must be at home. 简的房间里开着灯。她一定在家。
3. must与have to的区别must侧重于说话者的主观看法，认为有必要或有义务去做某事Everyone must keep the law. 人人都要守法。have to 则重于客观需要，含有“不得不”“被迫”之意The last train has gone. We’ll have to walk home. 最后一班车已经开了，我们得走回家了。从时态方面看，must 只有现在时一种形式，而have to则有多种时态形式。
如：You will have to show your papers at the gate. 在大门口你得出示证件。
【典型错题】If you know nothing about the famous program called Where are we going, dad?, you _____ be living in a box!
A. would B. can C. must D. need【错因分析】
本题的关键是对语境的理解，对句意的把握会直接影响能否正确判断空格处所缺情态动词的意思。其次，如果没有掌握选项中四个情态动词的用法，也会影响正确作答。
【思路点拨】首先要理解题干中句子的意思，然后弄清楚四个选项中情态动词的用法，再结合句意判断空格处要表达的是肯定推测“一定是”，再结合选项得出正确答案。
【正确答案】正确答案为C。句意：如果你对《爸爸去哪儿了》这个著名的节目一无所知，那你一定是生活在盒子里。根据上文提示此空是表示肯定的推测，“一定是”要用情态动词must，故选C。
【中考链接】
1. (2018 重庆)You _______ stop when the traffic lights(交通灯) turn red.
A. can'tB. may C. mustD. needn't
【答案】C解析：句意：交通灯变红时你______停车。A. can’t不能，B. may可能，C. must必须，D. needn't不必，根据句意，答案选C。
2. (2017 福建) —Mum, may I go swimming now?—Yes, dear, but remember that you ______ go with your dad.
A. mayB. canC. must
【答案】C解析：句意：——妈妈，我现在可以去游泳吗?——是的，亲爱的，但是记住你必须和你爸爸一起去。may可以；can可能；must必须。根据语境可知这里用must。故选C。
3. （2017 黔西南州）—Must I leave now? It’s still raining hard outside.—No, you ______.You can wait till the rain stops.
A. don’t have toB. couldn’tC. can’tD. shouldn’t
【答案】A解析：句意：——我必须现在离开吗？外面还在下雨。——不，你不必．你可以等到雨停。don't have to不必；couldn't不能；can’t不能；shouldn’t不应该。在回答以must开头的一般疑问句时，肯定回答用Yes, sb. must，否定回答用No, sb. needn't或don't have to，结合句意，答案选A。
【闯关提分训练】must和have to
1. —Can you go shopping with us this afternoon?—Sorry, I can’t. I ______ look after my little sister.
A. can B. may C. have to
2. —May I smoke here?—No, you ________. This is a no-smoking room.
A. needn’t B. mustn’t C. need D. wouldn’t
3. Someone is knocking at the door. It ______ be my mother. It’s time for her to be back.
A. can B. may not C. must D. mustn't
4. You _____ take me to the station. My brother’s taking me.
A. can’t B. mustn’t C. shouldn’t D. don’t have to
5. — Sorry, Miss Liu. I left my workbook at home. Must I hand it in(上交它) today?— No, you ______. You ______ bring it here tomorrow.
A. mustn’t; should B. can’t; must C. mustn’t; may D. needn’t; can
6. —Excuse me, sir, visiting hours(探视时间) are over. You _____ leave.—Pardon me(对不起), nurse. I didn’t hear the bell(铃声).
A. may B. can C. must D. need
7. The children ______ play basketball on the road.
A. can’t B. can C. mustn’t D. must
8. You ______ go and see a doctor at once because you got a fever(发烧).
A. can B. must C. dare D. would
9.—Mum, must I finish the homework now?—No, you ______.You can do it after supper
.A. needn'tB. mustn't C. can'tD. may not
10. (2018 盐城一模）Sorry! I can't follow you. I ____ finish my homework first.
A. can B. may C. must D. could
11. (2018·济南三模) —Must I answer the question in English?—No, you _______.
A. can'tB. mustn't C. needn't D. shouldn't
12. Yesterday it rained heavily when school was over. We _____ stay in our classroom
A. mustB. shouldC. had toD. need
13. I can’t go with you. I ______ stay at home until my parents come back.
A. canB. mayC. mustD. could
14.—Must I finish the work today?—No, you ______. But you ______ finish it next Monday.A. mustn’t; mustB. needn’t; mustC. mustn’t; couldD. needn’t; could
15. —______ you ______ wear your sports shoes for P.E. class?—Yes, we do.
A. Have; toB. Do; haveC. Do; have toD. Does; have to
16. —May I go out now, Dad?—Well, you _________ finish your school work first.
A. canB. mayC. needD. must
17. —Why can’t Nancy come to your party?—Because she ______ do her homework.
A. canB. can’tC. has toD. doesn’t have to
18. (2018 河西区一模) Mike _____ finish the work at once. He can finish it tomorrow.
A. must B. have to C. shouldn't D. doesn't have to
19. We shouldn't arrive late for class. We ______ be on time.
A. mustB. mayC. couldD. can
20. It is in the library. You __________ talk loudly.
A. may notB. wouldn't C. needn't D. mustn't
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