高中英语语法情态动词讲解精致版讲解随手练

学习好资料欢迎下载学习好资料欢迎下载学习好资料欢迎下载情态动词一、情态动词用法**情态动词具有词汇意义，但意义不够完整，一般不能单独作谓语。情态动词表示说话人的语气和态度。can;could;may;might;shall;should;will;would;must;dare;need;oughtto**主要归纳为以下几个考查热点：1.情态动词基本用法；2.情态动词表示推测和特定的语气；3.情态动词+havedone结构；4.情态动词和各种时态连用的含义；Hemaybeateacher.Hemaybereadingintheclassroom.Hemayhavefinishedherhomework.Itmusthavebeenrainingheavilywhenhegotback,forhewaswetover.1.can的用法①表示现在的能力（相当于beableto）He______/_____________readFrenchfluentlynow.注：1)can的主语是人或物,beableto的主语是人e.g.She_________singthesonginEnglish.Thismachine____makeyoufeelcomfortable.2)表示特定的某一过去能力或表示成功地做了某事时，只能用was/were

able

to，

不能用could。He

_____escapefrom

Europe

before

the

war

broke

out.②表示对现在的推测（只用于否定句和疑问句中，肯定句中用may/might）A:Look,someoneiscoming.Who______itbe?B:It_____betheheadmaster.A:It_______behim.HehasgonetoBeijingonbusiness.B:Thenit_______beMr.Zhang.Helooksliketheheadmaster.③用于肯定句中表示【客观上或理论上】的可能性，“有时候可能会”（不是推测）Childrencanbeannoyingsometimes.Accidentscanhappenonsuchrainydays.④用在否定句、疑问句、感叹句中常表惊讶、怀疑、不相信的语气。Howcanyoubesocareless?Whatcanhepossiblymean?⑤表示请求和允许----CanIgonow?----Yes,youcan./No,youcan’t.【在推测可能性方面的must＞may＞might＞can’t】参考答案为：①can/isableto;1)can/beableto;can;2)was

able

to

②can;must;can’t;maycould的用法①表示过去的能力，可用________________________替换。（注意后者还有另一个意思）He_________/________________rideabikewhenhewasonly7.②表示委婉的请求(注意回答用词)----CouldIuseyourcomputer?----Certainly,youcan.参考答案为：①was/wereableto;②could;wasableto3.may/might的用法**may①表示请求或许可;MayIaskyouaquestion?②表推测（可能性小；常用于肯定句或否定句中，不用于疑问句中）Hemaybealawyer.Hemaynotbealawyer.**might①表委婉的请求;----MightIaskyouaquestion?----Surely,youmay.----May/MightIsmokeinthisroom?----Yes,youcan.(No,youcan’t/mustn’t.)②表推测（可能性比may还小）Hemightbealawyer.**may用于祈使句,表示祝愿.MayyouryearsatColumbiabethehappiestofyourlife,andmayyoublossomintojustwhatyoudreamtobe.希望在哥伦比亚大学学习的四年成为你一生中最快乐的时光！祝愿你梦想成真！Maythehopeandinspirationwereceivefromyoubegivenback.Mayyoureturnsafeandsound.Mayyoubehappy! 4.must的用法①“必须”_________表示禁止，“千万不可以；不准”在表“必须”这个意思之下，须要注意对于must一般疑问句的回答---Mustwecleantheclassroomnow?---Yes,you________./No,you_______/________________.②表示推测，“肯定，一定”，只用于肯定的陈述句中Hemustbealawyer.他一定是个律师；他现在不可能在家，因为昨天他去了美国。判断：Hemustn’tbeathome,becausehewenttoAmericayesterday.()在表“必定，一定”这个意思之下，尤其需要注意must有关的反意疑问句1)Youmustbejoking,__________?2)Hemustbealawyer,__________?3)Hemustbedoinghishomeworkupstairsnow,__________?4）Hemusthavearrivedalready,__________?5）Hemusthavearrivedyesterday,_________?6）Hemusthavefinishedtheworkbytheendoflastmonth,_________?7）Itmusthaverainedlastnight,_________?③“非要，偏要，一定要”----Whoisthegirlstandingthere?----Well,ifyou______know,hernameisMabel.参考答案：①mustn’t;must;needn’t/don’thaveto；②判断：错误的写法：其中mustn’t要改为can’t；反义疑问句：1）aren’tyou;2）isn’the;3）isn’the;4）hasn’the(若句中不含任何时间状语，即可用对应的现在完成时完成反意疑问句);5）didn’the(若句中含有过去的时间状语，用一般过去时完成反意疑问句);6）hadn’the(若句中含有过去完成时的时间状语，用过去完成时完成反意疑问句);7）didn’tit③must;5.shall的用法①用于【第一、三人称】的疑问句中表示说话人征求对方的意见或向对方请示；ShallIhelpyoucarrythatbox?_______hewaitoutsideorcomein?②用于【第二、三人称】的陈述句中表示说话人给对方的承诺、警告、威胁、强制、命令等语气。Ifyouworkwell,youshallhavehigherpay.（承诺）Ifyouwon’tdoasItellyou,youshallnotgototheparty.（威胁）Peopleunder18shallnotbeemployedinnightwork.（强制）Ifyoudon’tgetout,Ishallknockyoudown.（警告/威胁）③Let’sgotogether,____________?Letusgotogether,______________?参考答案：①Shall;③shallwe;willyou.6.should的用法①表示义务，“应该，应当”，用于各种人称Youshouldbepolitetoyourteacher.Youshouldn’tspendsomuchtimeplayingcomputergames.②根据以往的经验或事实做出合理的推断，“照说应该,想必，估计”Iftheystarttoday,theyshouldarrivethereintwodays.Itis12o’clock,andIshouldbehomeintenminutes.IwonderwhereMaryis.Sheshouldbeherenow.**Should用于if引导的条件状语从句中表示某件事情的可能性很小，意思是“万一”。---WhatcanIdoforyou?---IfyoushouldseeMr.Smith,givehimmyregards.③在某些从句中(如与“建议”、“要求”、“命令”相关的名词性从句)，表示虚拟语气．Itissuggestedthatwe(should)makebetteruseoftheschoollibrary.Itishightimethatwe_______/___________theproblem.④表惊讶、遗憾的语气，“竟然”Itisapitythatsheshouldhavelostallhismoney.Itissurprisingthatheshouldbesofoolish.参考答案：③solved/shouldsolve(固定句式Itishightimethatsb过去时/should+动词原形；是某人做某事的时候了。Should不可以省略。)7.will的用法①表示目前的表示某种倾向或习惯性动作。Hewillsitthereforhours,reading.EverySaturdayeveningtheywillplaychesstogether.Boyswillbeboys.②表示意志，意愿IhavemadeupmymindtogoandIwill.Iwilldomybesttohelpyou.注意下面这句话：If

you

will

read

the

book,

I´ll

lend

it

to

you.

如果你愿意读这本书，我会把它借给你。8.would的用法①表示过去的习惯性动作（不表状态）OnSundayshewouldcometoseehisagingparents.Heusedtobeaquietboy.()Hewouldbeaquietboy.()②委婉的请求----___________youdomeafavor?----Ofcourse,I_________.Wouldyoupleasetellmehowtogettothezoo?③表意愿（will的过去式）Itoldhimnottogobuthewouldn’tlistentome.④用于虚拟语气中Ifhewereintown,hewouldhelpyou.(______________________________)Ifyouhadcomeearlier,youwouldhaveseenhim.(______________________________)参考答案：①√;×②Would;will;④对现在的虚拟；对过去的虚拟9.dare的用法①情态动词一般用于否定句、疑问句、条件状语从句中，后接动词原形，一般现在时中，谓语动词无三单。过去式为dared。She

_______

out

alone

at

night.

她晚上不敢一个人出去。Not

one

of

them

________

mention

this.

他们谁也不敢提这件事。

Thatwaswhyhe______doso.那就是他为什么敢这样做的原因。②实义动词daretodo;don’t/doesn’t/didn’tdaretodo过去式为dared。Jack______theriver.Helookedafraid.A.darenottocrossB.darednotcrossC.darednottocrossD.doesn’tdaretocross参考答案：①darenotgo;dared;dared;②B10.need的用法①情态动词。仅用于否定句和疑问句中，肯定句中一般用must,oughtto,should代替；词形只有一个，没有将来时、过去时或第三人称单数形式，后面接动词原形。②实义动词。needtodo；don’t/doesn’t/didn’tneedtodo过去式为needed。----_________Ifinishtheworktoday?----Yes,you__________./No,you____________.“need”作为实义动词时，通常用法是：sb＋need＋todosth＋need＋doing=sth＋need＋tobedone请看下面的例子：1．WeneedtocollecttheparcelbeforeweleaveforEngland．去英国之前，我们需要收拾好行李。2．Weneedtotellhimthetruth．我们需要告诉他真相。3．Mycarneedsrepairing．我的汽车需要修理。4．Theflowersneedwatering．这些花需要浇水。5．Hisleathershoesneedstobemended．他的皮鞋需要修补。6．Herroomneedscleaning．她的房间需要打扫。参考答案：②Need；must；needn’t/don’thaveto11.“情态动词+havedone”结构含义①_________________过去一定做过某事②_________________过去可能做过某事③________________过去不可能做过某事④_________________过去本应该做某事却未做⑤_________________过去本不应该做某事却做了⑥_________________过去本不必做某事却做了⑦_________________过去有能力/条件做某事却未做参考答案：①musthavedonesth;Itmusthaverainedlastnight,forthegroundiswet.②may+have+done用于肯定句中。—WhathashappenedtoGeorge?—Idon'tknow.Hemayhavegotlost.③can’thavedonesth.Mr.Smithcan'thavegonetoBeijing,forIsawhiminthelibraryjustnow.④should/oughttohavedonesth.Tom,youaretoolazy.Theworkshouldhavebeenfinishedyesterday.IoughttohavegonehomelastSunday.我理应上星期日回家.⑤shouldn’t/oughtnottohavedonesth.Look,Tomiscrying.Ishouldn'thavebeensoharshonhim.Yououghtnottohavegivenhimmorehelp.你不应该帮助他那么多.⑥needn’thavedonesth.Ineedn'thaveboughtsomuchwine—onlyfivepeoplecame.我本来没有必要买这么多酒，只来了五个人。⑦could(不用can)+havedone.Hecouldhavepassedtheexam,buthewastoocareless.二、巩固练习()1.----HasJohnarrivedyet?----No,she__________anhourago.A.oughttocomeB.musthavecomeC.shouldcomeD.oughttohavecome()2.----I’msorry,I________atyoutheotherday.----Forgetit.Iwasabitoutofcontrolmyself.A.shouldn’tshoutB.shouldn’thaveshoutedC.mustn’tshoutD.mustn’thaveshouted()3.You_____notgetmysupportifyoudosuchathing.A.shallB.must C.should D.dare()4.Hearingthestepsofthepolice,thethief_______moveatall.A.daresnotB.darednottoC.didn’tdaretoD.notdare()5.Tom,you____leaveallyourclothesonthefloorlikethis!A.wouldn’tB.mustn’tC.needn’tD.maynot()6.----Ihearyou'vegotasetofvaluableAustraliancoins.___Ihavealook?----Yes,certainly.A.DoB.MayC.WillD.Should()7.––Shelooksveryhappy.She_____havepassedtheexam.––Iguessso.It’snotdifficultafterall.A.shouldB.couldC.mustD.might()8.ItisusuallywarminmyhometowninMarch,butit________berathercoldsometime.A.mustB.canC.shouldD.would()9.MyMP4isn’tinmybag.Where_____Ihaveputit?A.canB.mustC.shouldD.would()10.John,lookatthetime.________youplaythepianoatsuchalatehour?A.MustB.CanC.MayD.Need()11.----I'vetakensomeoneelse'sgreensweaterbymistake.----It__________Harry's.Healwayswearsgreen.A.hastobeB.willbeC.mustn'tbeD.couldbe()12.----Didyoulistentothespeech?----No,we________it.Butwehadalotoftrafficonourway..A.musthaveattendB.shouldn’thaveattendedC.couldattendD.couldhaveattended()13.----________wefinishalltheexercisesinclass?----Yes,you__________.A.Shall;willB.Need;canC.Can;mightD.Must;must()14.----What’sthename?----Khulaifi.________Ispellthatforyou?A.ShallB.WouldC.CanD.Might()15.Don'tbeworried.Thenews__________betrue.A.maynotB.mustn'tC.needn'tD.shan't()16.Somewarm-bloodedanimals__________hibernate.A.neednotB.doesnotneedtoC.needn'ttoD.donotneed()17.Hedidn'tagreewithmeatfirstbutI___________persuadehim.A.wasabletoB.wasableC.couldD.couldbeableto()18.I________havebeenmorethansixyearsoldwhentheaccidenthappened.A.shouldn’tB.couldn’tC.mustn’tD.needn’t()19.Allthedoctorsinthehospitalinsistedthathe______badlyillandthathe______atonce.A.shouldbe;shouldbeoperatedonB.shouldbe;wasoperatedonC.was;shouldbeoperatedonD.was;wasoperatedon()20.Weareallforyoursuggestionthatthediscussion______.A.beputoffB.wasputoffC.shouldputoffD.istobeputoff()21.Nooneanswersthephonecall.They______.A.musthavegoneoutB.can’thavegoneoutC.shouldhavegoneoutD.needn’thavegoneout()22.----Idon’tmindtellingyouwhatIknow.----You______.I’mnotaskingyouforit.A.mustn’tB.maynotC.can’tD.needn’t()23.----Mum,IclimbedtogettheTeddyBearfromthetopoftheshelf.----Mygoodness!You______yourself.You______dothatnexttime.A.musthavehurt;can’tB.shouldhavehurt;mustn’tC.couldhavehurt;mustn’tD.can’thavehurt;needn’t()24.Hedidnotagreewithmeatfirst,butintheendI______persuadehim.A.wouldB.couldC.mightD.wasableto()25.----Mustwehandinourhomeworkbeforeweleave?----No,you______.A.mustn’tB.needn’tC.havetoD.can’t()26.Canyouimaginethatasmartmanlikehim______makesuchastupidmistake?A.mightB.shouldC.wouldD.need()27.WhenthepoetwasstudyingatCambridgeUniversity,he______takeawalkalongthefamousrivereverymorning.A.willB.couldC.shallD.would()28.----MayIsmokehere?----Ifyou______,chooseaseatinthesmokingsection.A.shouldB.couldC.mustD.may()29.You______getanewbikeifyoudoverywellinthecomingexam.A.shallB.willC.shouldD.must()30.Hedidnotregretsayingwhathedidbutfeltthathe______itdifferently.A.couldexpressB.wouldexpressC.couldhaveexpressedD.musthaveexpressed情态动词专项练习1.——Don’tforgettobringmynewbookstomorrowafternoon.

——No,I＿＿＿＿＿＿＿.

A.don’tB.can’tC.won’tD.couldn’t

2.Ihearyou’vegotasetofAustraliancoins.＿＿＿Ihavealook?

——Yes,certainly.

A.DoB.MayC.ShallD.Should

3.Heseldomlistenstoothers.He＿＿＿＿＿answerforwhathehasdone.

A.shallB.willC.canD.would

4.——MayIleavetheofficebefore5o’clockintheafternoon?

——No,I’mafraidyou＿＿＿＿＿＿＿.

A.needn’tB.shouldn’tC.mustn'tD.won’t

5.——ShallItellJohnaboutit?

——No,you＿＿.Idon’tknowhistelephonenumber.

A.needn’tB.wouldn’tC.mustn’tD.shouldn’t

6.MrBushisontimeforeverything.How＿＿＿itbethathewaslatefortheopeningceremony?

A.canB.shouldC.mayD.must

7.Thetrafficlightisred,soI＿＿＿stopmycar.

A.mustB.havetoC.canD.mustn’t

8.——Whathappenedtotheyoungtreesweplanted?

——Thetrees＿＿＿well,butIdidn’twaterthem.

A.mightgrowB.needn’thavegrown

C.wouldgrowD.wouldhavegrown

9.Iwasreallyanxiousaboutyou.You＿＿＿homewithoutaword.

A.mustn’tleaveB.shouldn’thaveleft

C.couldn’thaveleftD.needn’tleave

10.Children＿＿＿＿＿＿＿＿inpublicveryoften.

A.shouldbepraisedB.shouldn’thavepraised

C.shouldn’thavebeenpraised

D.shouldn’tbepraised

11.Let’scleantheclassroom,＿＿＿＿＿＿＿?

A.won’tyouB.shallweC.doweD.willnotyou

12.Tom＿＿＿＿＿＿＿showhisexamresultstohisparents.

A.darenotB.daredC.daretoD.daresnotto

13.Idon’tthinkhe＿＿＿＿＿＿＿anewbike.

A.needtobuyB.needsbuyC.needD.needbuy

14.——Nacy＿＿＿＿theletterfromhermother.

—No,shecan’thave.Thepostmanhasn’tcomeyet.

A.canreceiveB.canhavereceived

C.musthavereceivedD.mustreceive

15.She＿＿thefilm.Sheknowsnothingaboutit.

A.can’tseeB.can’thaveseen

C.mustseeD.mustn’thaveseen

16.Theymusthavebeenherethedaybeforeyesterday,＿＿＿＿?

A.mustn’ttheyB.didn’tthey

C.mustn’thavetheyD.hadthey

17.——Ididn’tseeheryesterday.

——Oh,butyou＿＿＿＿＿＿＿＿＿＿＿.

A.musthaveB.oughtto

C.shouldhaveD.cannothave

18.——MustItakeabus?

——No,you＿＿＿＿.Youcanwalkfromhere.

A.mustnotB.don’t

C.don’thavetoD.hadbetternotto

19.—Whydoyoumakemedoso?

—Iamsorrythatyou＿＿＿＿＿dosuchathing.

A.wouldB.canC.shouldD.may

20.—Willyoustayforlunch?

—Sorry,＿＿＿.Mybrotheriscomingtoseeme.

A.Imustn’tB.Ican’tC.Ineedn’tD.won’t

21.Whatwouldhavehappened＿＿＿＿,asfarastheriverbank?

A.ifBobhaswalkedfartherB.ifBobshouldwalkfarther

C.hadBobwalkedfartherD.ifBobwalkedfarther22.Youdidn’tletmedrive.Ifwe＿＿＿＿inturn,you＿＿＿sotired.

A.drove；didn’tgetB.drove；wouldn’tget

C.weredriving；wouldn’tget

D.haddriven；wouldn’thavegot

23.Withoutelectricityhumanlife＿＿＿＿quitedifferenttoday.

A.isB.willbeC.wouldhavebeenD.wouldbe

24.Oh,Janne,you’vebrokenanotherglass.Youought＿＿＿＿whenyouwashedit.

A.becarefulB.tocare

C.havecaredD.tohavebeencareful25.I＿__oftengofishingwhenIlivedinthecountryside.

A.shouldB.wouldC.couldD.might

26.He＿＿＿＿＿＿ratherstayathomethangotothecinemawithyou.

A.shouldB.mightC.wouldD.hadbetter

27.It’shightimewe＿＿＿＿＿tothetheater.

A.willB.shallC.aregoingtoD.went

28.——CouldIuseyourtelephone?

——Yes,ofcourseyou＿＿＿＿＿＿＿＿＿.

A.couldB.willC.canD.might

29.It’sstrangethatthey＿＿＿＿＿nothingaboutthismatter.

A.knowB.wouldknowC.knowsD.knew

30.Iwishyou＿＿＿＿＿＿gowithmetomorrow.

A.willB.wouldC.shallD.can

31.——DoyoustillrememberthedaywhenwewenttotheGreatWall?

——Ican’trememberitwell,but＿＿＿＿＿＿sometimelastautumn?

A.mightitbeB.couldithavebeen

C.coulditbeD.mustithavebeen

32.——Ican’tgetthroughtothegeneralmanager’sofficeanyhow.

——Thelineisbusy.Someone＿＿thetelephone.

A.mustuseB.uses

C.musthavebeenusingD.mustbeusing

33.Hesuggestswe＿＿＿＿＿＿tothecinemaatonce,otherwisewewillbelate.

A.mustgoB.goC.willgoD.wouldgo

34.Whenapencilispartlyinaglassofwater,itlooksasif＿＿＿＿.

A.breaksB.hasbroken

C.werebrokenD.hadbeenbroken

35.Thegeneralorderedthatthethief＿＿＿＿.

A.bepunishedB.wouldpunish

C.wouldbepunishedD.shouldpunish

36.IfonlyI＿＿＿＿＿howtooperateacomputerasyoudo!

A.hadknownB.wouldknow

C.shouldknowD.knew

37.Itissurprisingthathe＿＿＿＿atthemeeting.

A.wasB.beC.isD.were

38.Ifyou＿＿＿＿waitamoment,I’llgoandfindourmanager.

A.canB.shouldC.willD.must

39.——Doyouthinkhewilldomeafavor?

——AsfarasIknow,heisthelastonetohelpothers.He＿＿＿＿bepreparedtogiveyouahand,though.

A.mightB.mustC.canD.should

40.EventhoughI’dhurtmyleg,I＿＿＿＿＿＿swimbacktotheriverbank.

A.couldB.mightC.hadtoD.wasableto

41.You＿＿＿＿＿＿＿gotothepartyifyoudon’tfinishyourhomeworkfirst.

A.won’tB.don’tC.oughtn’tD.shan’t

42.——Itisrathercoldhere.Shallwelightafire?

——No,we＿＿＿becausethingsareeasytocatchfire.

A.won’tB.can’tC.mustn’tD.needn’t

43.I＿＿＿＿＿＿ProfessorJoneshadtaughtmethisquestion.

A.believeB.deeplythinkC.wishD.suppose

44.Thechairmanrequestedthat＿＿＿＿＿＿＿.

A.themembersstudiedtheproblemmorecarefully

B.theproblemsweremorecarefullystudied

C.theproblemscouldbestudiedwithmorecare

D.themembersstudytheproblemmorecarefully

45.I＿＿＿＿＿＿itagain.

A.wouldlikeyoutoread

B.wouldlikethatyouread

C.wouldlikeyoureading

D.wouldlikeyouread46.Ifyoureallywantyourselftobeingoodhealth,youmust＿＿＿always＿＿＿somuch.

A.not；besmokingB.not；havesmoked

C.not；tosmokeD.benot；smoking

47.IfI＿＿＿you,I＿＿＿＿moreattentiontoEnglishidiomsandphrases.

A.was；shallpayB.am；willpay

C.wouldbe；wouldpayD.were；wouldpay

48.“Wouldyouhavetoldhimtheanswerhaditbeenpossible?”

“Iwouldhave,butI＿＿＿＿sobusythen.”

A.hadbeenB.wereC.wasD.wouldbe

49.Hehadanexpressionofresentment（不高兴）,asifMartin＿＿＿afoolofhim.

A.hadmadeB.makesC.madeD.wouldmake

50.＿＿＿＿thefog,weshouldhavereachedourschool.

A.BecauseofB.InspiteofC.IncaseofD.Butfor

51.Therewasahalfsmileonhisfacewhichsuggestedthathe＿＿＿＿happytohavegivenhislifeforhiscountry.

A.wasB.shouldbeC.wouldbeD.were

52.Weallagreedtohersuggestionthatwe＿＿＿＿＿＿totheGreatWallforsightseeing(观光).

A.willgoB.goC.shallgoD.shouldhavegone

53.Youmustbeastudent,＿＿＿＿＿＿＿＿you?

A.wasn’tB.areC.mustn’tD.aren’t

54.Theyoungmaninsistedthathe＿＿＿＿＿nothingwrongand＿＿＿free.

A.did；setB.haddone；shouldbeset

C.do；besetD.haddone；mustbeset

55.Withoutyourhelp,I＿＿＿＿theexamlastterm.

A.failedinB.wouldhavefailed

C.wouldn’tpassD.wouldfail参考答案及解析

1.C。will在此表示“应诺”。

2.B。MayI...?中的may用以表示“允许、许可”。

3.A。shall用于第二、三人称的肯定句或否定句，表示说话人的意愿，有“命令、警告、威胁、强制、允诺、决心”之意。

4.C。may表示“允许”。回答may引起的问句，肯定式一般用Yes,ofcourse.／Yes,certainly.／Sure.／Yes,youmay.否定式用No,youmustn’t.

5.A。needn’t表示“不必要”；mustn’t表示“禁止”；wouldn’t表示“拒绝”。

6.A。can表示“可能性”，通常用于否定句或疑问句中，且有时还带有“惊奇、不相信”等感情色彩。

7.B。must表示说话人的主观愿望，而haveto多表示客观需要。

8.D。wouldhavedone表示对过去已发生的事情的推测，表示“可能……”。

9.B。shouldn’thavedone表示“过去本来不应该做某事而事实上已经做了”。

10.D。should／shouldnot＋do，表示“（现在）应该／不应该……”。

11.B。Let’sdosth.表示“建议做某事”，含听话一方在内，故用shallwe。如果用Letusdosth.结构，则用willyou?表示请求对方允许。

12.A。情态动词dare的过去式为dared，常用于否定句、疑问句及条件句中，没有人称和数的变化，否定式是在dare后接not，再接动词原形。dare作为实义动词时，有人称和数的变化，构成否定句时，前要加助动词，后接带to或不带to的动词不定式。13.D。need作为情态动词，一般用于否定句、疑问句及条件句中，后接动词原形。表示“现在不必干某事”,用neednotdosth.；表示“过去不必干某事”，用neednothavedone。need作为实义动词,与其它动词用法相同，用于否定句或疑问句要加助动词。

14.C。“musthavedone”结构，表示对过去发生情况的肯定推测。

15.B。can’thavedone，表示对过去发生情况的否定推测，意为“不可能已经……”。

16.B。musthavedone表示对过去发生情况的肯定推测，句中带有明确的过去时间状语，故附加疑问句用“didn’tthey”。17.C。should／ought