By the time 用法详解
?by the time意为“到……时候（为止）”，是一个介词短语，在句中经常起连词作用，引导时间状语从句。它的主要用法如下：
? 1. 如果从句中的谓语动词是一般过去时，那么主句中的谓语动词通常用过去完成时，表示“截止到从句动作发生时，主句动作已经完成，即过去的过去”。例如：?By the time he returned home，the rain had stopped.
? By the time I got to the station，the train had already gone。
? 2. 如果从句中的谓语动词为一般现在时/或现在完成时（表示将来），那么主句中的谓语动词常为将来完成时，表示“截止到将来某一时间为止，主句动作将已经完成”。?By the time you get back，I shall have finished the work.
? By the time I graduate next year, I will have lived here for 5 years. ? By the time of next term , we will have learned 3000 words.
? 3. 如果主句动作不强调已经完成，只是说明某个时候的状况，（主句是be的系表形式或者是表示像know, find, believe等表示认知的持续性动词，则往往用一般时态，不用完成时态。）此时主句不用完成时，而应根据实际需要选用适当的时态，此时by the time相当于when。例如：
? He was out of breath by the time he reached the top.
? By the time the bus came，so many people were waiting that it was a free fight to get on it. 公共汽车来的时候，等车的人很多，成了一场挤车的混战。?By the time he went abroad, he was fourteen.出国那年他14岁。
?By the time the war was over , death and suffering were to be seen everywhere.?在战争结束的时候，到处可见死亡和饥饿。这里没有“死亡和饥饿”已经完成的意思，只是描述当时这个时间点的状况。所以用过去时。
?巩固练习：
? 1. （2005天津卷） By the time Jane gets home， her aunt _____for London to attend a meeting.
? A. will leave B. leaves
? C. will have left D. left
? 2. By the time you have finished this book, your meal ___ cold.(2012四川卷)
? A. gets B. has got C. will get D. is getting
? 3. （2009北京卷） When I talked with my grandma on the phone， she sounded weak， but by the time we _____ up， her voice had been full of life. ? A. were hanging B. had hung
? C. hung D. would hang
? 4. ―Did you see Xiao Li at the party
?―No，_____by the time I arrived.
? A. she’d left B. she’s left
? C. she was left D. she must leave
? 5. By the time I saw the angry expression on his face，I_____ what I had to face.
? A. knew B. have known
? C. would know D. had known
6.（2008四川卷） The telephone_____， but by the time I got indoors，it stopped.
A. had rung
B. was ringing
C. rings
D. has rung
?7.（2008山东卷） By the time he realizes he _____into a trap， it’ll be too late for him to do anything about it.
? A. walks B. walked C. has walked D. had walked
情态动词用法总结如下表
学法提炼
If they _________ to do this work, he might do it some other way.
A. were
B. should
C. will
D. can
2. I was told yesterday that the company _________ me to Rome next week for a business conference.
A. should have sent
B. were going to send
C. should be sending
D. should send
3. Let’s take a walk, ________
A. will we
B. don't we
C. do we
D.
shall we
4. He was a good swimmer so he _________ swim to the river bank when the boat sank.
A. could
B. might
C. should
D. was able to
5. I went to the doctor's yesterday, I had to wait for half an hour before he ________ see me.
A. can
B. may
C. might
D.
could
6. ---- _________ this book be yours ---- No, it ________ not be mine. It ________ be his.
A. Can, must, may
B. May, might, must
C. Can, may, must
D. Must, can, may
7. ---- "We didn't see him at the le cture yesterday.”
---- “He _________ it.”
A. mustn't attend
B. can't have attended
C. would have not attended
D. needed have attended
8. They _________ the plane, or perhaps they have been prevented from coming for some reason.
A. can have missed
B. may have missed
C. can have lost
D. may have lost
9. Since the ground is white, it _________ last night.
A. had snowed
B. must have snowed
C. must be snowing
D. must have been snowing
10. You must be fifty, ________
A. mustn't you
B. needn't you
C. aren't you
D. mayn't you
11. You must have seen him off yesterday, _________
A. haven't you
B. didn't you
C. mustn't you
D. needn't you
12. ---- That must be a mistake.
---- No .it _________ be.
A. can't
B. isn't able to
C. can
D. was able to
13. He had known the matter before you told him, so you _________ have told it to
him.
A. mustn't
B. can't
C. needn't
D. shouldn't
14. How ________ so
A. dare you to say
B. dare you say
C. do you dare say
D. dare to say
15. You are their teacher. You _________ care of them.
A. should to take
B. might to take
C. ought to take
D. need to take
16. She is studying medical science now but she _________ a lawyer.
A. used to be
B. would be
C. were
You return the book now. You can keep it till next week if you like.
A. can't
B. mustn't
C. needn't
D. may
not
2. I wish I ______ to the moon one day.
A. can fly
B. an able to fly
C. could fly
D. was
able to fly
3. If my lawyer ______ here last Saturday, he __ me from going.
A. had been; would have prevented
B. had been; would prevent
C. were; would prevent
D. were; would have prevented
4. If it _____ for the snow, we ____ the mountain yesterday.
A. were not; could have climbed
B. were not; could climb
C. had not been; could have climbed
D. had not been; could climb
5. Without electricity human life quite difficult today.
A. is
B. will be
C. would have been
D.
would be
6. Jenny _______ have kept her word. I wonder why she changed her mind.
A. must
B. should
C. need
D.
would
7. We ________ last night, but we went to the concert instead.
A. must have studied
B. might study
C. should have studied
D. would study
8. —Could I borrow
your dictionary？
—Yes, of course you ________ .
A. might
B. will
C. can
D.
should
9. —If he ______ , he _______ that food.
— Luckily he was sent to the hospital immediately.
A. was warned; would not take
B. had been warned; would not have
taken
C. would be warned; had not taken
D. would have been warned; had not
taken
10. I told Sally how to get here, but in fact, I her, for she had been here a short time before.
A. needn't tell
B. didn't need to tell
C. needn't have told
D. didn't need to have told