1 I can speak good English. 我能够讲很好的英文。
2 You should study English. 你应该学习英文。
3 Women can do anything when jealous.
4 It's strange that you should say this.
5 We should be grateful if you could do it.
6 He might come.
7 1）I would be happy to help you.
2）I am happy to help you.
这里说I would be happy to help you.要比I am happy to help you.委婉得多。
在例句1）中，would表达一种委婉假设的含义，意思是说“如果你真的需要我帮忙，我会很乐意帮助你的”。这么用would来说这句话，只是告诉对方你主观上愿意帮助他。至于对方是否需要你来帮助，那是他的选择。在例句2）中，说am就显得比较直截了当，不给对方选择的余地，好像在强迫别人找你帮忙一样，有点把自己的主观意愿强加于对方的感觉（impose yourself on people who don't want your help）。比如，也许对方真的是需要有人帮忙，但他出于自尊心的原因不一定非得找你帮忙。所以，用例句2）也许会让人感觉你把自己当作救世主一样，但例句1）就绝不会让人有这种误解。
笔者曾经告诉自己的一个外国朋友笔者正在写英语语法书，他在电子邮件里回复说：I would be happy to have a read.他这么说的言外之意是：如果笔者愿意把自己的书稿通过电子邮件发给他看看的话，他会非常乐意拜读一下的。他这里用would be happy这么说就显得非常礼貌，没有强迫笔者非得把书稿发过去给他看的意思。如果他说I am happy to have a read.则显得他很想让笔者把书稿发给他看，有点强人所难的意味。
8 Let me see if I could help work this out.
这里的could表示非常礼貌和谦虚。即使你认为对方的某个问题是小菜一碟，你能轻而易举地解决，你也不妨用could来显示你的谦虚谨慎。比如，你是公司新来的一名员工，大家对于某个电脑技术难题都无法解决，而你很清楚该怎么处理。面对那么多的公司老前辈和领导，你只是一个初出茅庐的新手，如果你很骄傲地说I can work this out. It's a piece of cake.（这个我能解决，对我来说简直是小菜一碟。）这样说就显得你过于自负，当然会让你的领导及其他老员工脸面上很难堪。但如果你用could说Let me see if I could work this out.则显得你为人谦虚，这样给周围同事的感觉自然大不一样。另外，万一这个问题你也解决不了，你用could这样委婉地表达也是给自己留了余地，因为could表明了你不肯定是否能完成。由此可见，can与could在语气上的巨大差异。这里的could在中文里也没有很好的对应词，不是一个简单的“能够”就能表达could的含义的。
9 I wouldn't pay them a penny.
5 Please read this article.
6 We hope that you will come and have lunch with us tomorrow.
7 You come and sit here, please.
8 I suggest that you have a word with him.
9 You may like to read this article.
10 We were wondering whether you could come and have lunch with us tomorrow.
11 Would you come and sit here, please?
12 You might want to have a word with him.
13 I would suggest that you have a word with him.
14 May I suggest that you have a word with him?
15 1）That's impossible.
2）Unfortunately that wouldn't be possible.
16 1）It is a good idea to agree on a price before we go any further.
2）Wouldn't it be a better idea to agree on a price before we go any further?
在例句1）中，谓语动词用的是is，it is a good idea表示“……这样做好”，用这种方式来向对方提出建议，显得有些自负而傲慢，有把自己的观点强加于对方的味道。在例句2）中，首先，借助would来“软化”生硬的口气。其次，把肯定句变为否定句，给对方很大的选择余地。再次，用否定的wouldn't来提问，更具商量的口吻。第四，把good变成better也显得更礼貌。
17 1）We can't go higher than 7 per cent.
2）We would find it (quite) difficult to go any higher than 7 per cent.
18 1）We need a commitment from you now.
2）We would like some kind of commitment from you now.
19 1）You'll have to pay more if you want that.
2）You may have to pay slightly more if you (really) want that.
20 1）It will be difficult to get my boss to agree to this.
2）It might not be very easy to get my boss to agree to this.
在例句1）中，用will显得语气比较强硬。在例句2）中，用委婉的might，表示“或许”来缓和语气。其次，把difficult改成not very easy，给对方的感觉更好。
21 1）We should spend more time looking for a compromise here.
2）Shouldn't we spend a little more time looking for a compromise here?
3．在表示过去的能力时，could与was/were able to的区别；
1．We are enjoying our holiday, though the weather (could, must) be better.
2．We (could, might) go to that new restaurant opposite the cinema.
3．How about going to the theater instead. We (could, should) go to the theater instead.
4．I don't know how she knows, but Mom (can, may) always detect when I'm lying.
5．Nobody else is going to turn up now for the lesson, so you (have to, may as well) go home.
6．No member of the association (shall, will) remove official documents from these premises without written permission.
7．The peace conference (may, has to) find a solution to the problem.
8．Rule 6. No member (shall, should) enter the bar area wearing sports kit.
9．The heating comes on automatically. You (must not, don't have to) turn it on.
10．It's a lovely hotel. And the staff (couldn't, might not) be more helpful.
11．You (could, may) be right, but I still don't agree with you!
12．I am sure Nick wasn't there. That (can't have been, shouldn't have been) Nick that you saw.
13．You (had to give, might have given) me a hand!
14．I caught a later train because I (had to see, must have seen) a client.
15．I suppose Bill (should have lost, might have lost) his way.
16．I don't know who rang, but it (could, must) have been Jim.
17．The situation was bad but it (could be, may have been, could have been) worse.
18．It's a pity you didn't ask because I (could help, could have helped) you.
19．It's your own fault, you (can't have, shouldn't have gone) to bed so late.
20．I was so angry that I (might, may) have killed her.
21．You screamed in your sleep last night. You (might have, might have had) a terrible dream.
22．Harry studies a lot. He (should know, should have known) all the answers.
23．It's possible that we'll know the answers tomorrow.
A．We may know all the answers tomorrow.
B．We should know all the answers tomorrow.
24．It's possible that the decision will be announced next week.
A．The decision might be announced next week.
B．The decision will be announced next week.
25．I know. Why don't we go out to eat instead.
A．I know. We must go out to eat instead.
B．I know. We could go out to eat instead.
26．Perhaps these are the keys.
A．These might be the keys.
B．These must be the keys.
27．I think it's wrong for you to work so hard.
A．You don't have to work so hard.
B．You shouldn't work so hard.
28．You needn't come if you don't want to.
A．You won't come if you don't want to.
B．You don't have to come if you don't want to.
29．It would be quite wrong for us to lock the dog in the house for a week.
A．We'd better not lock the dog in the house for a week.
B．We can't lock the dog in the house for a week.
30．I don't think you should ring him now. It's rather late.
A．You might not ring him now. It's rather late.
B．You'd better not ring him now. It's rather late.
31．Peter wasn't here, so he_______(break) your vase.
32．I'm sure Jack didn't mean to ignore you. He_______(notice) you.
33．That was a lucky escape! We_______(kill)!
34．The meat is a bit burnt. You_______(cook) it for so long. I did tell you!
35．There were plenty of tickets left for the concert. We_______(buy) them in advance.
36．Sally got home at four o'clock this morning. The party_______(be) really good.
37．Thank you very much for buying me flowers. You______(buy) me flowers.
38．I don't believe that you have lost your keys again! You______(lose) your keys again.
39．Mary was a talented violinist at the age of ten. She_______(play) the violin very well when she was ten.
40．Perhaps they didn't notice the tire was flat. They_______(notice) the tire was flat.
41．Our worrying so much was a waste of time. We________(worry) so much.
42．It's possible that the last person to leave didn't lock the door. The last person to leave_______(lock) the door.
43．They hurried there, only to find the meeting was cancelled. In fact, they________(go) there.
44．She paid him and walked off. Then she realized that he_______(not, be) a deaf mute. How did she know? He must have heard her initial instructions or he_______(not, know) where to take her.
45．A: It seems to rain. I guess I________(bring) my umbrella.
B: It would be nice to have one but how________you_______(know) that this morning?
46．"If you sit too close to the television, you'll ruin your eyes." Sound familiar? You_______(hear) this warning as a child. People sit too close to the television because they already can't see very well. This may give them tired eyes or a headache, but it won't make their eyesight any worse.
47．As it turned out to be a small house party, we_______so formally.
A．needn't dress up
B．did not need have dressed up
C．did not need dress up
D．needn't have dressed up
48．You can't imagine that a well-behaved gentleman__________be so rude to a lady.
49．It has been announced that candidates________remain in their seats until all the papers have been collected.
50．It is unthinkable that he_________be so careless.
51．The boss has promised that every player in NBA__________have a rise in income.
52．A man wants to see you, sir._________he wait outside?
53．He was a good swimmer so he_________swim to the river bank when the boat sank.
D．was able to
54．Oh, I'm not feeling well in the stomach．I_________so much fried chicken just now.
B．mustn't have eaten
C．shouldn't have eaten
55．Several cases have been reported recently of people who________read and detect colors with their fingers.
56．No one expect his secretary_________go straight into his office without permission.
B．is able to
D．is not allowed to
57．She was absent for the first time yesterday. She_________sick.
D．must have been
58．He did very badly on the exam. He_________harder.
B．must have studied
D．should have studied
59．I________to him because he phoned me shortly afterwards.
A．ought to have written
B．must have written
C．couldn't have written
D．needn't have written
60．He_________ten lectures on American history, but he only gave two because of his illness.
C．must have given
D．should have given
61．We did hold a meeting yesterday, but you________. So we did not inform you.
A．did not need attending
C．did not need to attend
62．We came early and had to wait two hours before the ceremony began. We_______.
A．should not hurry
B．must not have hurried
C．need not hurry
D．need not have hurried
63．"Have you paid your telephone bill?"
"No, but I________yesterday."
A．ought to pay it
B．ought to have paid it
C．must pay it
D．must have paid it
64．He__________pull down a bull and acknowledged as a man with superman strength.
A．used to be able to
B．would be able to
C．should be able to
D．might be able to
65．Some women_________a good salary in a job instead of staying home, but they decided not to work for the sake of the family.
B．should have made
D．could have made
66．I didn't send out my application form last week, but I_______.
D．might have to
67．Mary_________my letter; otherwise she would have replied before now.
B．ought to have received
C．couldn't have received
D．shouldn't have received
68．You_________him so closely; you should have kept your distance.
C．couldn't have been following
D．shouldn't have been following