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1、1By 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
2、） ，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, bel
3、ieve 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 fou
4、rteen.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
5、. 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
6、4. Did you see Xiao Li at the party？ No，_by the time I arrived. A. shed left B. shes 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
7、 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， itll be too late for him to do anything about it. A. walks B. walked C. has walked D. had walked 2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 can not / cannot /cant docould1.表示能力（体力，技能）2
8、.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couldnt doCando? Yes,can.No,cant.may may not do Maydo? Yes,may. No,mustnt/cant.might可以（问句中表示请求）可能，或许（表推测）祝愿（用于倒装句中） might not do Mightdo? Yes,mightNo,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/mustnt do Mustdo? Yes,must.No,neednt/dont havehave t
9、o 只好，不得不（客观的必须，有时态和人称的变化） dont have to do Dohave to do? Yes,do. No,dont.ought to应当（表示义务责任，口语中多用 should）ought not to/oughtnt to doOughtto do? Yes,ought. No,oughtnt.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/shant do Shalldo?Yes,shall. No,shant.should 应当，应该（表义务责任）本该（含有责备意味） should not/shouldnt do
10、Shoulddo?will will not/wont dowould意愿，决心请求，建议，用在问句中would 比较委婉 would not/wouldnt doWill/Woulddo?Yes,will. No,wont.dare 敢（常用于否定句和疑问句中） dare not/darent do Daredo? Yes,dare.No,darent.need 需要，必须（常用于否定句和疑问句中） need not/neednt do Needdo? Yes,must. No,neednt.used to 过去常常（现在已不再）used not/usednt/usent to dodidn
11、t use to doUsedto do?Diduse to do?Yes,used. No,use(d)nt. Yes,did. No,didnt.3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”；canhave donecannot have done1) 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
12、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 done1) 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。neednt have done 表示做了本来
13、不必去做的事。注意：didnt 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。If they _ to do this work, he might do it some other way.A. were B. should C. will D.
14、 can2. 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 send3. Lets take a walk, _? A. will we B. dont we C. do we D. shall we4. He was a good swimmer so he _ swim to the river bank when th
15、e boat sank.A. could B. might C. should D. was able to5. I went to the doctors yesterday, I had to wait for half an hour before he _ see me.A. can B. may C. might D. could6. - _ 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, may7. - We didnt see him at the lectur
