Question：情态动词不太好学，读了你的上篇觉得很清晰，今天讲什么？
Answer： 今天我们继续学习情态动词（III）
Must/mustn’t, have/ don’t have to
Reading：
We are in the biology museum. The teacheris telling us some dos and don’ts. When you are visiting the museum, remember:
You must be quiet. If you have to askquestions, you can raise you right hand.
You must move together in line. You mustn’trun inside the museum.
You have to make some notes to help writethe reports afterwards.
I. Must, have to 句式的构成：
must：
现在式和将来式：
肯定句： I/ You/He/She/ It/ We/ You/ They must go.
否定句： I/ You/He/She/ It/ We/ You/ They mustn’t go.
疑问句： Must I/you/ he/ she/ it/ we/ you/ they go?
2.must 接不带to的不定式： I must go.
3.must 没有人称和数的变化: Imust go. He must go. We must go.
4. must的过去式用had to
have to
现在式：
I/You/We/ They have to go.
I/You/We/ They don’t have to go.
Do I/ You/We/ They have to go?
He/She/Ithas to go.
He/She/It doesn’t have to go. Have to go?
Does he/she/it have to go?
过去式： I had to go. I didn’t haveto go. Did I have to go?
将来式： I’ll have to go. I won’t have to go. Will I have to go?
II. Must， have to 的用法：
用 must, haveto 表示“必须”，“不得已”，有时用 must 和have to 没有区别：
You have to make some notes to help write the reports afterwards.
也可以说： Youmust make some notes to help write the reports afterwards.
III. Must 和have to 的区别：
Reading：
During the visiting, two of the students have a quarrel. The teacherhas to have a talk with them.
Student A: Do we have to have the talk now? I want to see more.
Teacher: Yes, we do. Must you have the quarrel inside the museum?
Student A: I’m sorry. What I want to do is feel the model of anelephant. I think I must feel it to see what its skin is like.
Student B: I think what he does is not allowed in the museum. I haveto stop him. I just tell him, “You mustn’t do it. It’s not allowed to feel thethings on show.”
Student A: But you don’t have to cry out to me.The teacher has told us we mustn’t talk loudly here in the museum.
Teacher: You must try to think if there is any mistake on your ownside.
1.有时must 和 have to 有明确的界。 用must 来表示对自己或别人要尽的义务， 表示对自己或别人要尽的义务，表示的是个人的观点， 是主观的。
I think I must feelit to see what its skin is like. （Student A 认为这是必要的）
2.相对来说have to 表示的是来自别人认为你要尽的义务， 是客观的， 是不受说话人控制的。
I have to stop him. （Student B这么做是由于他认为博物馆的规定不能违反）
3.在疑问句中某事是必须的或不得已的，通常用DoI (you等) have to...? Must I(you等)...？句式则不常见。
Dowe have to have the talk now?
发生了某种与说话人意愿相反的不受欢迎的事时，疑问句中用must 可以表示“偏偏”，不需要回答。
Must you have the quarrel inside the museum?
4.否定式mustn’t he don’thave to/haven’t got to 意义不相同。Mustn’t 可用来表示叫别人不做什么，告诉别人某事是错的，是违反法律或规定的：
You mustn’t do it. Itis not allowed to feel the things on show.
The teacher told uswe mustn’t talk loudly here in the museum.
而用don’t have to/haven’t got to 则表示没有必要做某事：
But you don’t have tocry out to me.
IV. Have got to
Reading：
After the visiting, the teacher is having a talk with other teachersabout what has happened in the museum. “ I’ve got to have a talk with mystudents immediately after whatever unhappy thing happens. First, I’ve got tostop them when they have the quarrel. Then I hope they can get something fromwhat has happened. “
1. Have got to通常和have to 同义，它比have to 更口语化，在口语中常用：
I've got to have a talk with mystudents immediately after whatever unhappy thing happens.
也可以说I have to have a talk with my students immediately after whatever unhappy thing happens.
2.但谈到一个特殊而不是习惯性的情形时， 通常用have got to 而不是have to:
I’ve got to stop then when they havethe quarrel.（而不说I have to stop them.）
3.否定式 haven’t got to
小练习：Fill inthe blanks: have to 还是 must
you don’t__________ cry out to me. The teacher has told us we _______(not) talk loudlyhere in the museum.
Do we________ have the talk now?
_______ youhave the quarrel inside the museum?
上期答案：1. Can 2. May 2. Would
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