解讀“have to”與“must”的用法

王玉萍

have to意為“必須;不得不”

強調(diào)外界客觀因素要求主語“不得不做某事”，表示客觀上的需要，有人稱和時態(tài)的變化，其后接動詞原形。have to可用于多種時態(tài)，形式隨時態(tài)變化而變化，還可以用在其他情態(tài)動詞之后。具體用法如下：

1. have to后接動詞原形，意為“必須做……;不得不做……”。如：

We have no food home， you have to go and get some， Tom. 家里沒有食物了，湯姆你得去買一些來。

2. have to 有人稱、數(shù)和時態(tài)的變化，其第三人稱單數(shù)形式為has to，過去式形式為had to。如：

She has to help her mom make dinner. 她不得不幫她媽媽做晚飯。

I had to do my homework last night. 我昨晚必須做作業(yè)。

3. 含有have to， has to的句子需分別借助動詞do， does構(gòu)成疑問句或否定句。如：

Do they have to go now？ 他們必須現(xiàn)在回家嗎？

You don't have to go if you don't want to. 如果你不想去，你就不必去。

must意為“應(yīng)該，必須”，mustn't意為“不應(yīng)該，不準(zhǔn)，不允許，禁止”。

使用must應(yīng)注意以下幾點：

1. must表示主觀義務(wù)，意思是“應(yīng)該，必須，一定”，其否定式mustn't意為“不應(yīng)該，不準(zhǔn)，不允許，禁止”。而不表示“不必”。如：

We must get there before five o'clock. 我們必須在五點前趕到那里。

You mustn't be late for school. 你千萬不要上學(xué)遲到。

對用must所提問題的否定回答，常用needn't或don't have to，意為“不必”。如：

Must I stay here after school？ 放學(xué)后我還要留在這里嗎？

No， you needn't / don't have to. 不，沒有必要。

—Must I clean all the rooms？ 我必須打掃所有的房間嗎？

—No， you needn't / don't have to. 不，你不必。

2. must表示推測，意為“一定，必定”（用于肯定句中）。

He must be our headmaster. 他肯定是我們的校長。

【鞏固訓(xùn)練】

I. 選擇填空。

1. At school I ___ wear a uniform and I___ keep my hair short.

A. can't; have to

B. have to; must

C. don't have to; must

D. does; has to

2. —Must I return the book this week？

—No， you ___. You can ___ it for 20 days.

A. mustn't： keep ? B. needn't; borrow

C. needn't; keep D. mustn't; borrow

3. —Can you please stay here a little longer？

—Sorry， I ___. I ___ eat dinner with my mother. She's coming.

A. mustn't; will have to

B. don't; have to

C. can't; had to

D. can't; have to

4. —___ does Jim ___ study hard these? ?days？

—He will take an exam next week.

A. How; have to ? ?B. Why; have to

C. What; have to ? D. When; has to

5. Mrs Green ___ go far if she goes shopping. The supermarket is beside her neighbourhood.

A. have to ? ? ? ? B. doesn't have to

C. needn't have to D. haven't to

6. This book ___ Tom's， because his name? ? is on the book.

A. maybe ? ? ? ? B. may be

C. must be ? ? ? ? D. must

7. The girl in the classroom ___ be Maria. She called me from the library just now.

A. mustn't ? ? B. may not

C. can't ? ? D. needn't

8. We ___ use mobile phones when the plane takes off.

A. may not ? ? ? B. couldn't

C. needn't ? ? ? D. mustn't

9. It's raining， so I ___ stay at home.

A. have to ? ? ? B. can't

C. don't have to ? D. needn't

10. —How do you usually go to school？

—My school is far away. I ___ take the bus to school.

A. need ? B. might

C. have to ? ? ? D. may

II. 按要求完成下列句子，每空一詞。

1. Zhang Lin has to clean her room on Friday.（改為否定句）

Zhang Lin ___ ___ ___ clean her room on Friday

2. Mary has to help her mother with cooking. （改為一般疑問句）

___ Mary ___ to help her mother with cooking？

3. They have to do some cleaning on Sunday. （對畫線部分提問）

___ ___ they have to ___ on Sunday？

4. Children ?must sit in the front seat of a car. （改為否定句）

Children ___ sit in the front seat of a car.

5. —Must I hand in （上交） my homework now， Mr. Smith？

—No， you ___. （否定回答）

III. 填入方框內(nèi)單詞，使句意完整通順，使用次數(shù)不限。

have to ?must ?can ?can't ?mustn't

1. I ___ arrive late for class. I ___ be on time.

2. I ___ keep my hair short and wear a school uniform.

3. I ___ listen to my teachers carefully in class. I ___ talk with my partner.

4. I ___ be noisy in the classroom. I ___ be quiet.

5. I ___ eat in the classroom. I ___ eat in the dining hall.