一、用must表示“必须”的意思时,通常着重于说话者的主观看法,认为有必要去做某事。而have to(has to)着重于客观需要,含有“不得不”的意思。比较下列句子:
We must study English hard.
我们必须努力学习英语。
You must be back no time.
你们一定要按时回来。
The children must go to bed before nine.
孩子们必须在九点前睡觉。
You are ill today. You have to see a doctor. 你今天病了,不得不去看医生。
二、用must表示“必须”,只有现在时态的形式。如果要表示过去时或将来时的“必须”,就要用have to的相应形式。如:
You mustn’t drive so fast.
你不要开这么快。
They will have to leave tomorrow morning.
他们必须明天早晨起程。
三、用于否定句时,must的否定式是“决不可、禁止”的意思,而have to的否定式(don’t have to或do not have to)是“不必”的意思。两者在意义上有较大的差异。若要表示“不必”这个意思,还可用needn’t。如:
You must water the flowers, but you needn’t do it at once.
你必须浇花,但不必马上浇。
I don’t have to (needn’t) but a new bike.
我不必买新的自行车。
四、must还可表示“肯定、必定”等表猜测的意思,have to则没有这种用法。如:
She is not here. She must go away.
她不在这里,肯定走了。
The bananas are black. They must be bad. 香蕉发黑,肯定坏了。
练习:
1. ——Mum, may I watch TV now?
——No, you ___________ finish your homework first.
A. mustn’t
B. must
C. have to
D. can’t
2. ——Must I finish that work today?
——No, you ________. You may finish it in three days.
A. shouldn’t
B. needn’t
C. mustn’t
D. hadn’t to
3. Yesterday it rained heavily when school was over. We _________ stay in our classroom.
A. must
B. should
C. had to
D. need
4. ——I can’t stop playing computer games.
——For your health, I’m afraid you _________.
A. can
B. may
C. must
D. have to
5. ——What did the headteacher say at the meeting?
——He said, “We _________ be proud of working hard. We mustn’t be lazy.”
A. must
B. needn’t
C. may
D. can’t
答案:
1—5 BBCDA
热文推荐:
联系客服