语法：情态动词must、have to 和have got to
情态动词must和have to都有“必须”的含义，它们的用法如下： （一）、 must “必须”、“应该”的用法:1.must 表示“必须”、“应该”。例如： ①We must protect our environment.(我们必须保护环境。） ②Everyone must obey the rule.（人人必须遵守制度。）
2. must的否定形式must not表示“不应该”、“禁止”、“不准”。语气比较强烈。例如：
①You mustn’t speak like that.(你不应该像那样讲话。） ②You mustn’t be late for school.（你不应该上学迟到。） 3.在回答must的问句时，肯定形式用must来回答，但否定形式用needn’t 或don’t have to来回答。而不用mustn’t来回答。例如：
①——Must I be home before 8 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，你必须。） （不，你不必。）
4.must还可表示推测，意思是“一定”、“必定”，一般只用于肯定句中。分三种情况：
1.）对于现在状态的推测，我们用：must +v.（状态动词或系动词），例如： ①He must be at home.(他准在家里。）
②There must be some children in the room.（房间里准有些孩子。） 2.）对于现在动作的推测，我们用：must +be + doing（行为动词），例如： ①They must be cleaning their room.(他们准是在打扫房间。） ②He must be watching TV.（他准是在看电视。）
3.）对于过去事实的推测，我们用：must +have +过去分词，例如: ①It must have rained last night.(昨晚准是下雨了。）
②I didn’t hear the phone. I must have been asleep.（我没有听到电话，我准是睡着了。）
（二）、have to 表示“必须”、“不得不”，例如：
①He has to stay in bed for 3 or 4 days.(他必须卧床休息三四天。） ②We will have to get up early tomorrow.（明天我们必须早起。）
（三）、have got to是 have to的口语形式。例如： ①I’ve got to leave for Nanjing.(我不得不去南京。)
*Must与 have to的区别：
must表示的是说话人的主观看法，而have to则表示的是客观需要。Must一般只有现在时，而have to有更多的形式。
①I must go now.(主观看法)
② My mother is ill, so I have to go now.(客观需要)
*Have to与 have got to的区别：
have got to虽然是have to的口语形式，但二者在用法上有严格的区别： have to的前面还可以用情态动词或助动词，而have got to却不可以； have to的否定形式为don’t/doesn’t /didn’t +have to,疑问式为Do/Does/Did + 主语 + have to…?而 have got to的否定形式是在have后加 not,疑问式把have提前。例如：
①We don’t have to go home. ①Do you have to go home? ②We haven’t got to go home. ②Have you got to go home?
一、.Fill in the blanks using have to, have got to, must, should, ought to, had better.
1.You _____________ not get down until the bus has stopped.
2.They _____________ be encouraged to speak English after class. 3.You often _____________ wait a long time for a bus.
4.We _____________ go and see Mary tomorrow, but I don’t think we will. 5.I _____________ not miss my train.
6.When traveling, you _____________ take care of your health.
7.In some parts of the world, you _____________ boil the water before drinking it.
8.If you have a stomach pain, you _____________ drink hot weak tea. 9.You _____________ not swim immediately after a heave meal. 10.You _____________ not wake me up when you come in. 11.He _____________ be ill, for he looks so pale.
12.You _____________ not have given him the money. 13.It’s getting late. I am afraid I _____________ go. 二、Choose the best answer. 1.----Must I do it now?
-----No, you _______. A. needn’t B. don’t have to C. mustn’t D. A or B 2.It’s nearly seven o’clock. Jack ______be here at any time. A. must B. need C should D can.
3.------When can I come for these photos? I need them tomorrow afternoon. -------They ____be ready by 12:00. A. can B. should C. might D. need 4.Sorry, I’m late. I ________ have turned off the alarm o’clock and gone back to sleep again. A. might B. should C. can D. will 5.I told Sally how to get there, but perhaps I ________ for her.
A. had to write it out B. must have written it out C. should have written it out D. ought to write it out
6.Jenny ________ have kept her word. I wonder why she changed her mind. A. must B. should C. need D. would
7.Tom ought not to ________ me your secret, but he meant no harm. A. have told B. tell C. be telling D. having told
8.Sir, you ________ be sitting in the waiting room. It is for women and children only. A. oughtn’t to B. can’t be C. won’t D. needn’t 9.If you really want yourself to be in good health, you must ______always ______ so much. A. not, be smoking B. not, have smoked
C. not, to smoke D. be not, smoking
10.I didn’t hear the phone, I ________ asleep.
A. must be B. must have been C. should be D. should have been 11.I was really anxious about you. You ________ home without a word. A. mustn’t leave B. shouldn’t have left C. couldn’t have left D. needn’t leave 12.You’d better go at once, _________ you?
A. shouldn’t B. wouldn’t C. hadn’t D. couldn’t 13.She ought to be praised, _________?
A. ought she B. she ought C. oughtn’t she D. she oughtn’t 14.He _________ go there by train.
A. oughtn’t to B. oughtn’t C. ought to not D. didn’t ought to 15.--------Look, it_________ be Mr. Wang.
------------No, it _________ be him. He has gone abroad.
A. may; mustn’t B. must; may not C. must; can’t D. can; may not 三、Correct the mistake in each sentence: 1.You have better hurry up.
2.The taxi should arrive at 8:30, but it didn’t turn up.
3.That mustn’t be the postman---------it’s only seven o’clock.
4.People ought vote even if they don’t agree with any of the candidates.