Lesson 125-128 | 核心句型：喝茶、一个著名的女演员 | 语法点：情态动词must的用法、have to的用法、must与have to的区别、need的用法
must是情态动词，没有人称和数的变化，后面接动词原形。
表示"必须，应该"（表示义务或命令）：
表示"肯定，一定"（表示推测，用于肯定句）：
must的否定形式：
have to表示"必须，不得不"，有人称和时态的变化。
一般现在时：
一般过去时：
一般将来时：
否定句和疑问句：
| 区别 | must | have to |
|---|---|---|
| 语气来源 | 表示说话人的主观意愿或命令 | 表示客观的需要，有"不得不"的意味 |
| 人称变化 | 没有人称和数的变化 | 有人称、数和时态的变化 |
| 时态 | 只有现在时形式 | 有现在、过去、将来等多种时态 |
| 否定含义 | mustn't表示"禁止，不允许" | don't have to表示"不必" |
例句对比：
| 情态动词 | 用法 | 例句 |
|---|---|---|
| must | 用于肯定句，表示很有把握的推测"一定" | He knows a lot about computers. He must be a computer engineer. 他对电脑懂得很多，一定是个电脑工程师。 |
| can't | 用于否定句，表示很有把握的否定推测"不可能" | That man can't be Mr. Li. Mr. Li has gone to Beijing. 那个人不可能是李先生，李先生去北京了。 |
| may/might | 表示不太有把握的推测"可能，也许" | It may rain this afternoon. You'd better take an umbrella. 今天下午可能下雨，你最好带把伞。 |
对现在情况的推测：情态动词 + 动词原形
对正在进行的动作的推测：情态动词 + be + 现在分词
need作情态动词：
多用于否定句和疑问句，没有人称和时态的变化，后面接动词原形。
need作实义动词：
可以用于各种句式，有人称和时态的变化，后面接名词、动词不定式或动名词。
| 原形 | 过去式 | 过去分词 | 词义 |
|---|---|---|---|
| throw | threw | thrown | 扔，投 |
| understand | understood | understood | 理解，明白 |
| wake | woke | woken | 醒，叫醒 |
| wear | wore | worn | 穿，戴 |
| win | won | won | 赢，获胜 |
| write | wrote | written | 写，写作 |
| be | was/were | been | 是 |
| beat | beat | beaten | 打，打败 |
| become | became | become | 变成，成为 |
| begin | began | begun | 开始 |
| break | broke | broken | 打破，折断 |
| bring | brought | brought | 带来，拿来 |
| build | built | built | 建造，建筑 |
| buy | bought | bought | 买 |
| catch | caught | caught | 抓住，赶上 |
1. I ______ go to bed early tonight because I have an exam tomorrow.
2. She ______ stay at home to look after her little sister yesterday.
3. You ______ be tired after the long journey.
4. He ______ work hard to pass the exam.
5. We ______ follow the school rules.
1. must/have to 2. had to 3. must 4. has to/must 5. must/have to
1. He has studied English for many years. He ______ speak English very well.
2. That ______ be Mr. Wang. He has gone to America.
3. It ______ rain tomorrow, so you'd better take an umbrella.
4. She is not here. She ______ be in the library.
5. You have worked all day. You ______ be very tired.
1. must 2. can't 3. may 4. may/must 5. must
1. You ______ talk loudly in the library.
A. mustn't B. don't have to C. needn't
2. He ______ go now, because his mother is waiting for him.
A. must B. have to C. has to
3. ______ I finish the work today? No, you needn't.
A. Must B. Have to C. Can
4. That man ______ be our teacher. Our teacher is much taller.
A. must B. can't C. may
5. You ______ worry. Everything will be all right.
A. mustn't B. needn't C. can't
1. A 2. C 3. A 4. B 5. B
1. I have to get up early every morning.（改为否定句）
2. She has to finish her homework before 8 o'clock.（改为一般疑问句）
3. You must come here before 9 o'clock.（改为否定句，表示"不必"）
4. He must be sleeping now.（改为否定句，表示"不可能"）
5. We had to stay at home last night because of the bad weather.（改为一般疑问句）
1. I don't have to get up early every morning.
2. Does she have to finish her homework before 8 o'clock?
3. You needn't come here before 9 o'clock. / You don't have to come here before 9 o'clock.
4. He can't be sleeping now.
5. Did you have to stay at home last night because of the bad weather?
1. 我必须现在就走了。
2. 他昨天不得不呆在家里照顾生病的母亲。
3. 你一定是饿了，吃点蛋糕吧。
4. 你不必担心，我能照顾好自己。
5. 那不可能是玛丽，她现在在上海。
1. I must leave now. / I have to leave now.
2. He had to stay at home to look after his sick mother yesterday.
3. You must be hungry. Have some cake.
4. You needn't worry. I can take good care of myself.
5. That can't be Mary. She is in Shanghai now.