Long may you live to enjoy it!
971 g．用在宾语从句中，表示希望或恐惧。
I hope he may（比will更正式一些）come．
I hope I may（比shall更正式一些）succeed．
I desire（or pray）that you may do something for her．
I trust this may meet with your approval．
I wish he may die．
He fears that（or lest）some accident may happen．
He is uneasy lest his son may get into trouble．
I hoped he might（or would）come．（如主句动词为过去时，应用might代替may）
He feared that（or lest）some accidents might（or would）happen．
972 h．用在that，so that引起的状语从句中，表示目的。
We work hard that（or so that，in order that）we may pay our debt．（=We work hard so as to［or in order to］pay our debt．）
Let the dog loose so that it may（or can，will）have a run（or so that it has a run）.
I brush my teeth so that I may keep them healthy．
主句谓语若为过去时，从句中应以might代替may（不过今天could，should，would比might用得更多）。
I stepped aside that she might enter．
I made haste that I might be on time．
They died that we might live．
973 i．Might可以用在表示现在情况或将来情况的虚拟条件句的主句或从句中，表示假想的情况。
If I might（=were permitted to）say anything，I would say those officials are corrupt．（But I know I may not say so．）
If he might work for you，you would be greatly satisfied．
If his father were a king，he might（=would be permitted to）do anything．（But his father is not a king，so he is not permitted to．）
If your terms were not so high，you might（=could easily）get a job．
We might（=would probably）miss the train［if we should wait any longer］．（条件从句有时可以省略）
974 j．Might也可用在表示过去情况的虚拟条件句中，这时要用might have这种形式，这种结构在主句中用得比较多。
If a boat had been lowered，he might have（=would probably have）been saved．（But I know it was not lowered，so he was not saved．）
If he had not wanted so high a salary，he might have got a job．
If his parents had only said “yes”，he might have（=could have easily）travelled over the world．
You might have had my assistance［if you had motioned it］．（条件从句有时可以省略）
Might have偶尔可用在条件从句中。
If I might have（=had been allowed to）killed anyone，I would have killed all of them．（But I know I was not allowed to kill．）
Even if I might have married four or five wives．I would have loved only one．
975 k．Might可用来代替may，表示现在情况，使语气显得谦逊温和。
I think he might get along with anyone．（肯定程度不强）
He might refuse your proposal．
Might it be possible?（客气的问句）
Might he forget his promise?
Might（比may更客气）I ask you a question?（但用得不是很多）
（但是：Could you answer me a question?）
Might I use the telephone?
You might（=I request you do）do me a favour．
You might go and see．
I might just as well（=had better）stay here．（建议）
You might try this medicine．
You might make a little less noise．（But you make so much noise．）（温和的批评）
They might not interfere too much．（But they do．）
You might help me．（But you do not．）
You might do it yourself．
Might have指过去情况。
He might have let us alone．（But he did not．）
It might well have been suggested earlier．（But it was not．）
You might have just as well reasoned with the tiger as persuade him．（和他讲道理是白费气力）
I might have gambled my fortune away．（But I did not．）（暗自庆幸）
I might have won a million in a lottery．（But I did not．）（遗憾）
7．Can，Could
976 Can，could可表示能力、可能性、同意等。
977 a．表示能力，可译为“能够”。
I can（=am able to）play tennis．（现在或经常性情况）
Mary can read and write．She can dance and sing．
Can you possibly do something for me?
I will help you if I possibly can get some money．
He cannot（或can not［若not需要强调时］）do anything for anyone，not even for himself or his family．
I can help you．（=I am in a position［or a situation or a condition］to help you．=It is in my power to help you．）
I could swim across a river long before．（过去情况）
I could swim across that river．（could也可指现在情况，如表示过去确实做了某事，可用was able to，succeeded in或managed to代替could，参阅965节。但could not可以用来表示过去的能力及动作）
He said that he could swim across the river．（=He said，“I can swim across the river．”）
Can't（help）but表示“只好”“不得不”。
I can't but（can't help but，can't choose but，can't do other than）tell her everything．（I have to do so．To tell her everything is all I can do．）
She can't help but believe it and weep．
“can't＋help＋动名词”表示“禁不住……”。
I can't help laughing（=I can't help but laugh）.
He can't help giving his life to her．
978 b．表示“可能性”（即客观上允许……），可译为“可以”。
We can（=may）go there by train，but cannot by boat．（It is possible for us to go there by train，but impossible by boat．）
You can buy it at any store．
We can eat and sleep in the hotel．
We can go to the seaside on Sunday．
“not...more than...can help”表示“尽量少……”。
Do not do anything more than you can help（=must）.
I will stay no longer than I can help．
Cannot...too可表示“怎样……也不会过分”。
One cannot be too honest（or over-honest，sufficiently honest，honest enough）.（=One should be as honest as possible．）
You cannot speak too highly of her beauty．（=Her beauty goes beyond your highest praise．）
I cannot thank you enough．
The importance of education can never be over-estimated．
979 c．表示“别人允许”，也可译作“可以”。
We children can（=may，are allowed to）smoke．
Father said we could do anything we wished．（间接引语）
I can enter the manager's office．
Children can enter elementary schools free of charge．
In this country we can say anything we like．
Can I throw the paper here?
You can't play all the time，John．
Can I go to the pictures，Mom?
980 d．表示“有（潜在）可能”，可译作“（有可）能”或“有时会……”。
Such an accident can happen．（只是在一定条件下偶尔发生）
A woman can do anything when jealous．
The weather here can be extremely cold．
Such an accident could happen．（这里could用来代替can，使口气显得不那么肯定）
He could be very rude．
A cat could be as fierce as a tiger．
The worst boy could be the best．
981 e．表示一种命令。
You can（=I want you to）buy me a pack of cigarettes．（你去给我买一包烟。）
You can scrub the floor，Mary．（玛丽，你来擦地。）
John can wait here until his mother returns．（约翰在这里等他妈妈回来。）
982 f．表示“某事是否是事实”，常用在疑问句及否定句中，在肯定句中要用may（可参阅969节）。在和表示状态的动词一起用时表示现在情况，在和表示动作的动词一起用时，表示将来情况。
Can this rumour be true?（=Is it possible that this rumour is true?）（谣言能是真的吗?）
I don't know．It may be true；it may not be true．
Yes，this rumour must be true．
No，this rumour cannot be true．（=It is impossible that it can be true．It must be false．）（这个谣言不可能是真的。）
Can he be ill?（他病了吗?）
I don't know．He may be．（我不知道，他可能病了。）
Yes，he must be．（是的，他肯定病了。）
No，he cannot possibly be，for I have just seen him．（不，他不可能病了，我刚才还见到他了。）
Can he be living in town?（=Is it possible that he is living in town?）（可用于进行时态）
I don't know．He may be living there；he may not be living there．
Yes，he must be living there．
No，he cannot be living there．
Can mom be still working in the kitchen?
I am not sure．She may not be．
Yes，she must be．It is lunch time．
No，she cannot be．I have just seen her going out．
Can this horse belong（表示状态的动词）to him?
It can't belong to him．
Can this hall hold a thousand men?
No，it cannot hold so many．
Can John believe such a story?
No，he cannot believe it．
Could this rumour be true?（could用来代替can，使口气显得谦逊）
Could he be ill?
He could not be living in town．
It could not hold so many men．
I asked whether this rumour could be true．（=I asked，“Can this rumour be true?”）（用于间接引语）
I thought he could not be living in town．（=I thought，“He cannot be living in town．”）
Can have可用来表示过去的情况。
Can he have said such a foolish thing?（=Is［or Was］it possible that he said such a foolish thing?=I doubt［or doubted］whether he said it．或者Is it possible that he has said such a foolish thing?）
I don't know．He may have said it，or may not have said it．
Yes，he must have said it．
No，he cannot have said it．（=It is［or was］impossible that he said it．或It is impossible that he has said it．）
Can I have borrowed his money?
I don't remember well．You may have borrowed it．
You must have borrowed it，because you had not enough money last month．
You cannot have borrowed it，because you spent very little money last month．
还可和一个表示过去时间的状语一起用。
Can he have come last Monday?（=Is［or Was］it possible that he came last Monday?）
He cannot have arrived yesterday．
Can he have finished his work by now?（=Is it possible that he has finished his work by now?）
He cannot have taken lunch by this moment．（=It is impossible that he has taken lunch by this moment．）
Could he have said such a foolish thing?（可用could代替can，使口气显得婉转一些）
You couldn't have borrowed it．
Could he have come last Monday?
I asked whether he could have said such a foolish thing．（=I asked，“Can he have said such a foolish thing?”）（用于间接引语）
I said he could not have arrived yesterday．（=I said，“He cannot have arrived yesterday．”）
Can he play you a trick?（=Is it possible that he will play you a trick?）（和一个表示动作的动词一起用，表示将来情况）
He may play me a trick．
He cannot play me a trick．
983 g．表示不耐烦或困惑等情绪，多用在修辞性问句中。
What can（=What on earth can）he mean?（他会是什么意思呢?）（不耐烦）
What can he want?（他会要什么呢?）
Where can he go?（他能到哪儿去了?）（困惑）
How can I answer that question?（感到难办）
What can I say?
984 h．用在表示目的的状语从句中。
He works hard so that he can（比may更口语化）pay his debt．
I study English in order that I can do business with foreigners over the world．
I stepped aside so that she could（比might更口语化）went in．
985 i．Could可用在表示现在、将来或一般情况的虚拟条件句中，在主句及从句中均可用。
If I could help you，I would do so．（But I cannot，so I will not do so．）
If John could run a machine，he might work in a factory．（But John cannot．）
If he were my friend，I could（=would be able to）do something for him．
I could be independent if I found some job．
If he had less children，he could not be so poor（=it would be impossible for him to be so poor）.
If it were not winter，the weather could not be so cold．
986 j．Could have可用在表示过去情况的虚拟条件句中，主句及从句中都可以用。
If I could have read and written（=had been able to read and write），I should have lived a happier life．（But I was not able to．）
If he could have convinced（=had been able to convince）you，you might have saved a lot of trouble．（But he was not able to．）
If I had known the address．I could have found out the house．（But I didn't know the address，so I was not able to find out the house．）
Even if he had tried his best，he could not have succeeded．
Even though he had worked harder，he could not have been rich（=It would have been impossible for him to be rich）.
987 k．Could可用来代替can，使语气显得更委婉客气。
Could（比can客气一些）you lend me your newspaper?（比较：Might I borrow your newspaper?）
Could you wait a little while?
Could he come and pick me up?
Perhaps I could do something．
At least I could say that．
Could有时表示“简直要……”。
I could（=feel inclined to）cry．
I could beat him．
I could eat three pigs．I feel so hungry．
Could have可用于含蓄条件句中（条件从句省略）。
I could have made a lot of money．（But you were opposed to the plan．）
We could have won the war．（But we were impatient．）
有时可用来表示温和的批评。
You could be more careful（=You're careless）.
You could have lent him the money．
He could have informed me days ago．
8．Must，Have to，Had to
988 Must，have to可用来表示“必须”“不得不”“一定（要）”这类意思。
989 a．表示“必须”。
You must（=should，ought to）do that．（=It is necessary for you to do that．）（讲话人的劝告）
We must love our neighbours．（道义上的需要）
You must pay the tax．（法律上的需要）
This leg must be cut off．（身体上的需要）
One must be industrious and frugal．（经济上的需要）
You must go by air．（其他方面的需要）
You must see her today．
You must work hard，or you will die．
You must work hard，if you want to live．
We must not hate even our enemy．（道义上不应当）
You must never steal．（法律上不允许）
You must eat nothing dirty．
You must（stressed）pay me at once．（=I insist that it is necessary for you to pay me at once．）（讲话人的强烈要求）
He must（stressed）at least let me know the situation．
You must marry and set up a family of your own．
This situation must not and shall not go on．
Applicants must have learned English four years．（必须学过……）
You must have done your homework before you can go out．（必须做完作业才能……）
He must have apologized before she can pardon him．（必须道歉之后她才会……）
带有must的问句表示征求对方的意见。
Must I go now?（=Do you think I must go now?）（我现在该走了吗?）
Must Jim wait for you tomorrow morning?（吉姆明早必须等你吗?）
Why must you fool about all day?（为什么你要整天胡混?）
Must I pay you before Sunday?（我一定要在星期天以前付你钱吗?）
有时表示“一定（要）”。
He must get（=insists on getting）back his own．（=He insists that it is necessary for him to get back his own．）（表示主语的强烈愿望）
If you must（stressed）marry my daughter，take her．
I am ready if you must fight．
We must needs（or must of necessity，must positively）fight to the last man．
I must and will stick to my principle．
Must he ask me to co-operate with him?
Must you be always meddling?
I replied that I must resign．（在间接引语中must可以不变）
He said I must go．
I thought she must marry a poor man like Dennis．
She knew that you must see her again．
即使不是在间接引语中，must也可表示过去的情况。
We were not allowed to retreat．We must march forward．
Everybody was busy，and one must always be doing．
990 b．在表示客观需要时，用have to和had to时比用must时多，可译为“不得不……”或“得……”。
Finding no other solution，she has to（=is forced to，is compelled to）commit suicide．（客观需要）
I've got to（VI语中代替have to，英国用法）see the doctor．（指一次动作）
I have to（指一次或多次动作）work today（or every day）.
Do you have to work everyday? I don't have to．
I got to（美式）marry him．Everything has been decided．
You have only（or but）to pay a few dollars and you may go anywhere by bus．（只需……）
I have only to say a word，and he will do everything for me．
I don't have to（=need not）pay anything．（不必……）
He hasn't got to（=need not）wait．
You don't have to work so hard．
I am having to defend myself．（现在进行时）
I had to do it，whether I liked it or not．（过去时）
I had got to marry him．Everything had been decided．（过去时）（在过去时中很少用got to，而用had to）
有时可用“be＋不定式”这种结构，表示类似的意思（比have to稍弱）。
We are to（=are destined to）work and suffer．There is no other way．（命中注定）
I am to do it，whether I like it or not．
A man is to work outside，and a woman is to work at home．
A person is to live a hundred years at most．
Must也可表示客观的必然性，可译为“总是要（会）”或“必然（会）”。
Competition must（=is sure to，cannot fail to）happen．
All men must die．
There must be a day for revenge．
War must be followed by hunger．
Must有时表示客观上令人不愉快的情况，与needs（副词）连用，可译为“偏偏……”，多指过去情况。
When I was sitting to dinner，the telephone must ring（=rang just to annoy me）.
Just as I was extremely busy，John must needs ask me a hundred and one questions．
When I wanted to pacify my mind，what had I to do but meet her again？（had to也可这样用）
