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贵的英语>济南五龙潭 back，I shall have finished the work.
• By the time I graduate垂的笔顺笔画顺序 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 en 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 e 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
情态 动词 | 用 法 | 否定式 | 疑问式 | 简答式 |
can | 1.表示能力（体力，技能） 2.允许或许可（口语中常用） 3.可能性（表猜测，用于否定句或疑问句中） 4.用于肯定句表示理论可能性 | can not / cannot /can’t do | Can…do…? | Yes,…can. No,…can’t. |
could | couldn’t do |
may | 可以（问句中表示请求） 可能，或许（表推测） 祝愿（用于倒装句中） | may not do | May…do…? | Yes,…may. No,…mustn’t/can’t. |
might | might not do | Might…do…? | Yes,…might No,…might not. |
must | 必须，应该（表主观要求） 肯定，想必（肯定句中表推测） | must not/mustn’t do | Must…do…? | Yes,…must. No,…needn’t/don’t have |
have to | 只好，不得不（客观的必须，有时态和人称的变化） | don’t have to do | Do…have to do…? | 入党申请书手写 Yes,…do. No,…don’t. |
ought to | 应当（表示义务责任，口语中多用should） | ought not to/oughtn’t to do | Ought…to do…? | Yes,…ought. No,…oughtn’t. |
shall | 用于一三人称征求对方意见 用于二三人称表示许诺、命令、警告、威胁等 | shall not/shan’t do | Shall…do…? | Yes,…shall. No,…shan’t. |
should | 应当，应该（表义务责任） 本该（含有责备意味） | should not/shouldn’t do | Should…do…? | |
will | 意愿，决心 请求，建议，用在问句中would比较委婉 | will not/won’t do | 海贼王女帝图片Will/Would…do…? | Yes,…will. No,…won’t. |
would | would not/wouldn’t do |
dare | 敢（常用于否定句和疑问句中） | dare not/daren’t do | Dare…do…? | Yes,…dare. No,…daren’t. |
need | 需要，必须（常用于否定句和疑问句中） | need not/needn’t do | Need…do…? | Yes,…must. No,…needn’t. |
ud to 结婚祝词 | 过去常常（现在已不再） | ud not/udn’t/un’t to do didn’t u to do | Ud…to do…? Did…u to do…? | Yes,…ud. No,…u(d)n’t. Yes,…did. No,…didn’t. |
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学法提炼
must have done | 表示主观上对过去已经发生的行为进行推测，意为“想必，准是，一定做了某事”; |
may/might have done | 表示对过去已发生行为的推测，意为“很有可能”； |
can…have done cannot have done | 1) could have done 用于对过去可能性的推断，意为“可能”，在肯定句中，指“某事可能是事实或可能会发生”；用于疑问句或否定句，表示对过去情况的怀疑、否定或惊讶； 2）could have done 意为“本来可以；差点就要”，指“某事可能发生但实际上未发生”常用于虚拟语气，表示惋惜、遗憾等； |
might have done | 表示“本来可能……，但实际上没有发生的事情”。另外，还可以表示“本来应该或可以做某事”之意，含有轻微的责备语气。 |
should/ought to have done | 1) 用于肯定句时，表示本该做某事，而实际上未做；用于否定句时，则表示不该做的事反而做了; 2) 用于对过去的推断，说话人认为“按理应当、理应如此”，说话人不能肯定，只是试探性地得出结论，语气婉转； 3) 对已发生的事表示“惊奇、失望、愤怒”等情绪。 |
needn’t have done | 表示做了本来不必去做的事。注意：didn’t need to do表示“没必要做而实际上也没有做某事” |
will/would have done | 用于推测过去，意为“想必、可以肯定”，指“说话人确信某事已发生，但并不确知”，并用于二、三人称： 1）如果以现在为时间点，可以用“will have done”； 2）如果以过去为时间点，只能用“would have done”； 3）will have done也用于推测将来某个时间前已经完成。 |
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If they _________ to do this work, he might do it some other way.
A. were 优秀教师简介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 nt B. were going to nd C. should be nding D. should nd
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 ________ e 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 尿不湿怎么用 D. Must, can, may
7. ---- "We didn't e him at the lecture yesterday.”
---- “He _________ it.”
