二、could的用法 can的过去式；
（用于虚拟语气，表示与事实相反的设想）能；可以； （表示可能性）可能； （用于婉转语气）能，可以 三、may的用法
1.表示请求和允许，意思是：可以
He may come if he likes. 如果他想来，可以来 2.表示祝愿，意思是：祝?，（但愿）。
May the friendship between our two peoples last forever. 祝两国人民的友谊万古长青。 3.表示推测，意思是：可能（会），或许（会）。
It may rain this evening. You'd better take an umbrella. 今晚可能要下雨，你最好带上雨伞。 四、must的用法 1.表“必须”。
You must talk to them about their study.你必须同他们谈谈关于他们学习的事。 2.在否定结构中表不许。
You mustn't leave here.你不能离开这儿。 3.表坚定的建议。
You must come and see us as soon as you get to Shanghai.一到上海你得马上来看我们。 4.表推测，暗含有很大的可能性，用在肯定句。
He must be ill. He looks so pale.他肯定是病了。他的脸色那么苍白。
注意： may 暗含的可能性较小。must 暗含的可能性较大。否定的猜测用can't The baby can't be ill. He is so active.那宝宝不大可能是病了。他那么活跃。 五、might的用法
might表示的可能性太小，没有足够的说服力去职责别人。
can, could 之间的区别，和 may,might 之间的区别在于，虚拟句和过去时态用后者，表示的可能性比原词小，但大部分时候2者可以互换，不会产生歧义或者对表述造成干扰。 六、should的用法
1.should 作为助动词 shall 的过去式，可以在间接引语中与第一人称主语搭配，表示过去将来时间。
2.should 作为情态动词，通常用来表示现在或将来的责任或义务，译作“应该”、“应当”，这时它可以和 ought to， be supposed to 互换使用。例如：
You should （= are supposed to ） complete your test in time. 你们应该按时做完你们的实验。
3.should 作为情态动词，可以用在条件状语从句中，表示语气较强的假设，译作“万一”、“竟然”，这时也可将 should 置于从句之首，即将 should 放在主语前面，而省略从属连词 if.
17
If it should rain tomorrow， I wouldn't go. （= Should it rain tomorrow， I wouldn't go.） 万一明天天下雨，我就不去了。 七、 would的用法
1.would是will的过去式，Would you like～？ 表示请求、劝说，是很客气的说法。
Would you like a cup of tea？ 您愿意喝杯茶吗？ 2.主语+would like to～
表示“想要??”的意思上，与?want to～意思一 样，但用此句型较客气。 I want to ask you a question. 3.最基本的虚拟语气句型:
主句用would/ should/ could/ might +动词原形。 八. ought to的用法
ought to 是一个可以加上to 的情态动词其意思与should是一样的,但是ought to 不能用于虚拟语气中表示推测,而should可以
ought to与should意思接近，大多数情况下二者可以互换，但是should谈的是自己的主观看法，ought to则更多反映客观情况，在谈到法律、义务和规定时使用。
如： We should／ought to help each other and learn from each other in our work． She is your mother, so you ought to support her．
We ought to go and see Mary tomorrow, but I don’t think we will．
情态动词练习
1. --- Where is Mary? --- She ____ in the library. A. should be B. must be C. can be D. must have been 2. His room is dark. He must ____ to bed.
A. go B. be going C. have gone D. have been gone 3. “Will your father stay home tonight?” “I’m not sure, He ____to work.” A. must go B. can go C. may be gone D. may be going 4. “Where is Tom?” “He isn’t here I think he ____ have gone home.” A. may B. must C. might D. A or B or C 5. “I think Helen is at home.”
“ No, she ____ be at home, for she phoned me from the airport just five minutes ago.” A. mustn’t B. needn’t C. can’t D. daren’t 6. He’s late. What ____ have happened to him?
18
A. can B. may C. should D, must
7. “ _____ he be watching TV now?” “Yes, he _____ be watching TV now.” “No, he _____ be watching TV now.”
A. Must; can; mustn’t B. Can; must; can’t C. Must; must; can’t D. Can; can; mustn’t 8. “____ he have left yesterday?” Yes, he ____ yesterday.” “No, he ____ yesterday.” A. Must; must have left; can’t have left B. Can; can have left; can’t have left C. Can; must have left; can’t have left D. May; must have left; shouldn’t have left 9. You must be a writer, ____ you?
A. mustn’t B. are C. must D. aren’t 10. You must have seen her yesterday, ____ you?
A. mustn’t B. haven’t C. didn’t D. don’t 11. You must have seen her, ____ you?
A. haven’t B. didn’t C. don’t D. A or B 12. There was plenty of time. She ____ worried or hurried.
A. mustn’t have B. shouldn’t have C. must be D. needn’t have 13. I got up early, but I ____ so because I had no work to do that morning.
A. mustn’t have done B. didn’t need to do C. needn’t have done D. can’t have done 14. I ____ up early this morning. So I stayed in bed till 9 a. m.
A. needn’t have got B. didn’t need to get C. shouldn’t have got D. can’t have got 15. The flower is dead. I ____ it more water.
A. will give B. would have given C. must give D. should have given 16. He ____ have come here yesterday, but he didn’t.
A. could B. should C. ought to D. A or B or C 17. “Must he do it?” “No, he ____.”
A. mustn’t B. needn’t C. doesn’t have to D. B or C 18. “Need you go now?” “Yes, I ____.” “No, I ____.”
A. need; needn’t B. must; needn’t C. may; mustn’t D. can; needn’t
19
19. “May I borrow your bike?” “No, you ____.”
A. mustn’t B. may not C. had better not D. can’t 20. “Can I do it?” “No, you ____.”or “No, please ____.”
A. can’t; doesn’t B. can’t; don’t C. can’t; can’t D. can’t; you don’t 21. I missed the last bus, so I ____ go home on foot.
A. must B. have to C. may D. had to 22. We ____ hurry if we want to arrive in time.
A. must B. need C. may D. have to 23. He ought to have won the first prize, ____ he?
A. oughtn’t B. shouldn’t C. mustn’t D. oughtn’t to 24. He ____ get up early when he lived in the countryside. A. would B. used to C. mustn’t D. can’t 25. My brother ____ be very naughty, and my sister ____ like reading.
A. used to; would B. would; used to C. used to; used to D. would; would 26. ____ you please pass on a message to him?
A. Do B. Shall C. May D. Will 27. ____ we set off now?
A. Shall B. Will C. Would D. ought 28. “____ he open the window?” Yes, please.” A. Does B. will C. Shall D. Would 29. I’ve told him many times, but he ____ listen to my advice.
A. shall not B. won’t C. will not D. wouldn’t 30. “Will you lend me a hand?” “Yes, I ____.”
A. will B. shall C. can D. may 31. Everyone ____ do his best for the modernization of China.
A. will you B. don’t we C. shall we D. do you 32. Let’s clean our room, ____?
20