英语语法学习中，对于虚拟语气的应用也是比较常见的。下面是小编给大家整理的英语语法的相关知识，供大家参阅!
英语语法：虚拟语气用在其它名词性从句中
1.虚拟语气用在suggest,demand,insist,ask,move,advise.desire,order,propose,require,recommend,request,maintain,vote等表示建议，命令，请求的动词后的宾语从句中，从句的谓语用should+原形动词，但美国英语中常要省去should。例如：
Isuggestwestartatonce.
Theyproposethatyou(should)readtherulescarefully.
Thecommanderorderedthatthesoldierfireattheenemy.
Heinsistedthathegothereonfoot.
Imovethatthemeetingbeadjourned.我提议休会.move:(在会议上)提议，动议
Example:
Heinsistedthatweall______inhisofficeatoneo39;clock.
a.beb.tobec.wouldbed.shallbe
Heaskedthatit______donerightaway.
a.isb.bec.shallbed.mustbe
HerecommendedthatJohn______withhim.
a.mustgob.wentc.willgod.go
2.虚拟语气用在Itis+形容词(或过去分词)+that....的主语从句中，表示要求，建议，提议，命令，请求等，英国英语中从句的谓语用should+原形动词(或完成式)构成，而美国英语中则要求用原形动词。该句型中常用的形容词或过去分词有：advisable,desirable,essential,important,better,keen,natural,necessary,probable,possible,strange,vital,desired,demanded,requested,suggested,recommended,required等。例如：
Itisnecessarythatthemachine(should)beoiledonceaweek.
Itisimportantthateveryone(should)obeythelaw.
Itissuggestedthatyoutakeawalkaftersupper.
Example:
Itisnecessarythathe______intimetoattendthemeeting.
a.comeb.camec.wouldcomed.needcome
Itwasproposedthatthematter______discussedatthenextmeeting.
a.wouldbec.willbec.wasd.be
Itisstrangethatshe______inthelastexamination.
a.shouldhavefailedb.havefailedc.wouldfaild.failed
3.虚拟语气用在与表示建议，要求，提议，命令，请求等意思有关的同位语从句和表语从句中，英国英语中要求从句谓语用should+原形动词，而美国英语中则要求用原形动词，但在asif,asthough引导的表语从句中，从句中谓语用动词过去式或过去完成式，表示对现在或过去的虚拟。例如：
Hecompliedwiththerequirementthattheexperiment(should)bedonetomorrow.
他同意明天再做实验的要求。虚拟语气用在其它名词性从句中
Helooksasifheweretired.他面带倦容。
Weagreetothesuggestionthatthey(should)workonnightshiftsinturn.
我们同意轮流值夜班的建议。
Hisorderisthatyou(should)sendthematerialstotheworksiteatonce.
他的命令是你们要把材料立即送到工地。
Example:
Youradvicethatshe______tillnextweekisreasonable.
a.willwaitb.isgoingtowaitc.waitsd.wait
Janeappearsasthoughshe______thesecret.
a.knowsb.hasknownc.hadknownd.knew
Helookedasifhe______illforalongtime.
a.wasb.werec.hasbeend.hadbeen
4.虚拟语气用在Itis(high,about)time(that)句型中，定语从句中谓语用动词过去式，意指将来。例如：
Itistime(that)wewenthome.
Itishightimewehadthemeeting.
Itistimeyouleft.
ItistimethatIwasoff.
注：如果主语是单数第一，三人称，动词be常用was。
Example:
We39;vebeensittingheredoingnothingaboutitfordays.It39;stimewe______theproblem.
a.shookhandswithb.gottobrasstackswith
c.gottogripswithd.reachedthebottomof
词组get(orcome)togripswith为开始努力对付。
Itishightimewe_______off.
a.areb.werec.bed.willbe
Itis______wedidsomethingaboutredecoratingthesittingroom.
a.hightimeb.longtime
c.goodtimed.full-time
练习题：
1.Thedoctorsuggestedthathe______ashortleaveofabsence.
a.willtakeb.wouldtakec.taked.took
2.Wedemandthatatomicweapons____.
a.beprohibitedb.willbeprohibited
c.areprohibitedd.oughttobeprohibited
3.Itwassuggestedthattransistors_____insuchdevices.
a.shouldbeusedb.shoulduse
c.canbeusedd.wereusing
4.Thetutorrecommendedthatshe_______thisbook.
a.mustbuyb.buy
c.shouldhaveboughtd.buys
5.Thehousemasterwasstrict.Herequestedthatwe______televisiononweeknights.
a.notwatchb.mustnottowatch
c.notbewatchingd.havenotwatched
6.MyfatherdidnotgotoNewYork,thedoctorsuggestedthathe______there.
a.nottogob.won39;tbe
c.notgod.notgoto
7.Idemandedthatthestudentseach______aplanforthesummervacation.
a.wouldmakeb.willmakec.maked.made
8.Itissurprisingenoughthatsuchahorriblething____there.
a.happenedb.willhappen
c.shouldhappend.hashappened
9.Itwasurgentthatshe______themasterimmediately.
a.callb.callsc.calledd.wouldcall
10.Helooksasifhe_____nothingaboutitbefore.
a.knowsb.hadknown
c.hasknownd.wouldn39;tknow
11.Myideaisthatwe______thechallenge.
a.oughtacceptb.willaccept
c.acceptd.areaccepted
12.Thesunrisesintheeastandsetsinthewest,soitseemsasifthesun______roundtheearth.
a.iscirclingb.hascircled
c.shouldcircled.werecircling
13.Itwassuggestedatthemeetingthateffectivemeasures_______tosolvetheproblem.
a.betakenb.mustbetaken
c.weretakend.take
14.It39;sadvisablethathe______withaclearlydefinedgoalinmind.
a.mustgob.goc.willgod.goes
15.Itseemedasifallofsuddentheanimal_____dangerintheair.
a.hassmeltb.hadsmelt
c.smeltd.wouldsmell
16.Itisbetterthatthebook______onthelowstool.
a.putb.puts
c.shouldbeputd.beput
17.Hemovedthatthereport______.
a.shouldacceptb.shouldbeaccepted
c.beacceptd.wouldbeaccepted
18.Theprofessorgaveordersthatthetest______before5:30.
a.befinishedb.willbefinished
c.willfinishd.shallfinish
19.It39;stimehe______somethingforhiscomingexamination.
a.dob.doesc.willdod.did
20.Itwasessentialthatallthenecessarydocuments______tothedean39;sofficebeforeFriday.
a.behandedinb.mustbehandedin
c.hadbeenhandedind.shouldhandin
21.Itishighlydesirablethatanewpresident_____forourinstitute.
a.appointedb.beappointed
c.hasbeenappointedd.isappointed
22.Thegovernmentorderedthatthepollutionproblemofthiscity______withinsixmonths.
a.wouldsolveb.wouldbesolved
c.shouldbesolvedd.mustsolve
23.Itisnaturalthatmuchresearch______toovercomecorrosion.
a.shouldmakeb.willmake
c.ismaded.shouldhavebeenmade
24.Itisimportantthataconsultantengineer______familiarwithmoderndevelopments.
a.isb.beingc.bed.hasbeen
25.Sinceherbloodpressureismuchhigherthanitshouldbe,herdoctorinsiststhatshe_____.
a.willnotsmokeb.isnotsmoking
c.didn39;tsmoked.notsmoke
英语语法：虚拟语气用在条件状语从句中
虚拟语气是一种特殊的动词形式，表示所说的话不是一个事实，而只是一种假设，愿望，建议，怀疑，猜测或不大可能实现的空想。
I.虚拟语气用在条件状语从句中
虚拟语气用在条件状语从句中，通常从句由连词if引导。
1.与现在事实相反的虚拟条件句
条件状语从句主句
If+主语+动词过去式主语+would,should,could,might+原形动词
(be的过去式用were)
例如：
IfIfeareddeath,Iwouldn39;tbeacommunist.
(刘胡兰)怕死就不做共产党员。
Iftherewerenoair,wecouldn39;tlive.
如果没有空气，我们就不能生活。
Example:
IwouldaskGeorgetolendusthemoneyifI______him.
A.hadknownB.knewC.haveknownD.know
I_____ittohimifIthoughthewouldunderstand.
A.shallexplainB.willexplainC.wouldexplainD.explain
2.与过去事实相反的虚拟条件句
构成
条件状语从句主句
If+主语+动词过去完成式主语+would,should,could,might+have+过去分词
例如：
Ifyouhadcomeafewminutesearlier,youwouldhavemethim.
如果你早来几分钟，你就会碰上他。
Iftherehadbeennoairinthetube,theresultoftheexperimentwouldhavebeenmoreaccurate.
如果试管中没有空气，实验结果就会更精确。
Example:
Ifyouhadn39;tgonewithTomtothepartylastnight,_______.
A.youwouldmeetJohnalready
B.youwon39;thavemissedJohn
C.youwillhavemetJohn
D.youwouldhavemetJohn
3.与将来事实相反的虚拟条件句
构成
条件状语从句主句
If+主语+should+原形动词主语+would,should,could,might或were+不定式+原形动词
例如：
Ifheweretocometomorrow,thingswouldbeeasier.
假如他明天会来，事情就容易办了。
Ifthesandshouldbebrokenup,itwouldgiveoutmuchenergy.
如果沙子能被分解，它会释放出大量的能量。
注：在表示与将来事实相反的虚拟条件句中，从句中的should有时可以省略。如：
Ifhemakethedesign,hemightdoitinsomeotherway.
要是他来搞这个设计，他可能用另外的方法设计。
Example:
Ifthesea____torise50feet,Indiawouldbecomeanisland.
A.willB.isC.wasD.were
Ifyou____toseeMary,whatwouldyoutellher?
A.areB.willbegoingC.mustD.were
Wemightstillcatchthetrainifwe___.
A.makehurryB.haste
C.makehasteD.hastily
4.错综时间的虚拟语气
在一些含有虚拟语气的句子中，如果主句与从句的谓语表示不同的时间，虚拟语气可有不同形式，即主句与从句各自按自己的时间构成虚拟形式。例如：
IfIhadmethimbefore,Icouldrecognizehim.要是我以前遇见过他，我就能认出他了。
(从句表示与过去事实相反，主句表示与现在或将来事实相反)
Ifweweredrivingataspeedof100Lianhour,wewouldhavearrivedthere2hoursago.如果我们的行车速度每小时100里，两小时以前我们就会到达那里了。
(从句与现在事实相反，主句与过去事实相反)
Example:
Ifyou_____thatlatemovielastnight,youwouldn39;tbesleepy.
A.haven39;twatched
B.didn39;twatch
C.hadn39;twatched
D.wouldn39;thavewatched
5.省略连词if
在条件状语从句中，如果有were,should,had，可以把连词if省去，把were,should,had放在句首，构成条件意义。例如：
Shoulditraintomorrow,whatwouldyoudo?万一明天下雨，你怎么办?
Weretherenofriction,wecouldnotwalk.要是没有摩擦力，我们就不能行走。
Hadweknownaboutthenewmethod,weshouldhaveapplieditearlier.
如果我们过去知道这种新方法，我们早就应用了。
Example:
HadAlicebeenmorehardworking,she_______.
A.hadnotfailedB.wouldnotfail
C.couldnotbefailedD.wouldnothavefailed
_______today,hewouldgettherebyFriday.
A.WouldheleaveB.Washeleaving
C.WerehetoleaveD.Ifheleaves
______difficulties,wewouldbesuccessful.
A.ShouldweovercomeB.Wouldweovercome
C.MightweovercomeD.Couldweovercome
6.虚拟结构中省略主句或从句
虚拟结构中有时可省去主句或从句，并不影响意义的完整。
(1)省去条件从句
Thatwouldbefine.那太好了。(省去了ifyouwouldcome或类似条件)
Iwouldn39;tpassupthechancetovisitChina.我不会放弃访问中国的机会。
Wemighthaveproducedmorecoal.我们可能生产出更多煤炭。
注：省略条件句，在试题中很少见到。
(2)省去主句，常用以表示愿望。从句谓语多用过去时或过去完成时。
Ifonlyshewerehere.假如她在这儿该多好啊!
Ifonlyhelived!假如他活着该多好啊!
IfonlyIhadknownitbefore.如果我早先知道这件事，那就好了。
Example:
Ifonlyit_____!butitistoolate.
A.isavoidedB.hasavoided
C.couldbeavoidedD.canbeavoided
Ifonlyeverything_____outaswewantedittoinlife!
A.isworkingB.worked
C.worksD.hasworked
英语语法：虚拟语气用在其它状语从句中
1.虚拟语气用在由asif,asthough引导的方式或让步状语从句中，一般情况下，如果主谓语动词为现在时，从句谓语多用过去时;如果主句谓语为过去时，从句谓语多用过去完成时。虚拟语气用在evenif,eventhough,whatever引导的状语从句中，从句谓语可参照由if引导的虚拟条件从句的谓语，一般用过去时或过去完成时。例如：
Thisoldmachinerunsasifitwereanewone.
Theoldworkerworksasthoughhewereayoungman.
Eventhoughshehadbeenhereverysoon,shewouldnotcatchthetrain.
Example:
Hehasjustarrived,buthetalksasifhe______allaboutthat.
a.knowb.knowsc.knownd.knew
Ican39;tstandhim.Healwaystalksasthoughhe_____everything.
a.knewb.knowsc.hasknownd.hadknown
______IusedalotofexamplesIstillcouldnotgetmyideaacross.
a.Sinceb.Butthatc.Nowthatd.Eventhough
2.虚拟语气用在sothat,lest(唯恐),incase(万一),unless,inorderthat(为了，以便),that(为了，以至于),forfearthat(生怕，以免),onconditionthat(如果)等引导的目的，条件状语从句中，从句谓语may或might+原形动词，也有用should,can,could+原形动词构成的。例如：
Theteacherexplainedthelawoncemoreinorderthatwemightunderstanditbetter.
Somepeopleeatsothattheymaylive.Othersseemtoliveinorderthattheymayeat.
一些人吃是为了生存，而另一些人似乎是活着就是为了吃。虚拟语气用在其它状语从句中
Ilefthimanotewithmyaddressonforfearthatheshouldnotknowwheretoseeme.
Theheroesgavetheirlivesthatwemightliveahappylife.
为了我们过上幸福生活，英雄们献出了自己的生命。
Example:
IncaseI______,Iwouldtryagain.
a.willfailb.wouldmissc.shouldfaild.shallmiss
Youshouldexercisevigilance_____youshouldbekilled.
a.sothatb.lestc.therefored.that
3.虚拟语气用在由whether引导的让步状语从句中，从句谓语用原形动词。例如：
Allenginesworkonthisprinciple,whethertheybelargeorsmall.
所有发动机都按这一原理工作，无论它们是大还是小。
Wemustfinishtheworkbeforewegohome,whetheritbeearlyorlate.
无论时间早晚，我们必须在回家前干完工作。
Allmatter,whetheritbegas,liquidorsolid,ismadeupofatoms.
所有物质，不论是气体，液体，或固体，都是由原子构成。
在此句型中，可省去whether，而将be放在主语前。例如：
Beitso,wemustcontinuetodothetest.
Wemustdoourbesttofulfilthetask,beiteversohard.
Example:
______I39;llmarryhimallthesame.
a.Wereherichorpoorb.Beherichorpoor
c.Whetherrichorpoord.Beingrichorpoor
练习题：
1.______,Imustdoanotherexperiment.
a.Itiseversolate
b.Eversolateit
c.Beiteversolate
d.Whetherbeiteversolate
2.Theyoungdriverlookedovertheenginecarefullylestit______ontheway.
a.goeswrongb.wouldgowrong
c.wentwrongd.shouldgowrong
3.Machinesareoftenoiledsothatthey______well.
a.ranb.runsc.shouldrund.running
4.Evenifhe______verybusy,hewouldhavekeptonlearningEnglish.
a.hadbeenb.wasc.wered.hadbeing
5.Supposingtheweather______bad,wherewouldyougo?
a.isb.willbec.wasd.were
6.______,hecouldnotsucceed.
a.However,hetriedthat
b.Hetriedhoweverhard
c.Howeverhecouldtry
d.Howeverhardhetried
7.Eventhoughtheenemy______wings,theycouldn39;tescapefromourencirclement.
a.hadb.hadhadc.haved.has
8.Shedescribedtheaccidentasifshe______itherself.
a.sawb.hasseenc.hadseend.sees
9.Hecametomeetusatthestationforfearthatwe______thewrongway.
a.takeb.shouldtakec.tookd.hadtaken
10.Thecarlookedverydirty,asthoughit______hundredsofmiles.
a.runb.runsc.hasrund.hadrun
11.Theteacherspokeslowlyinorderthatwe______nodifficultyinfollowinghim.
a.shouldhaveb.had
c.willhaved.didn39;thave
12.Allmagnetsbehavethesame,______theylargeorsmall.
a.howb.arec.bed.were
13.Atthebeginninghedidn39;twanttospeakEnglishlesthe_____mistakes.
a.willmakeb.shouldmake
c.wouldmaked.can
14.Irememberthewholethingasifit______yesterday.
a.happenb.happensc.happenedd.happening
15.Shestayedathomeforafewdayssothatshe_____hermother.
a.takescareofb.tookcareof
c.mighttookcareofd.mighttakecareof
16.Shetookupthemeterwithcareforfearthatit_____.
a.isdamagedb.tobedamaged
c.shouldbedamagedd.wasdamaged
17.Inmanycasestheheatingeffectisneglectedasifthere______noflowofcurrentalongthewire.
a.areb.werec.isd.being
18.I39;llputthemoneyonthetablejustincaseyou______it.
a.mightneedb.wouldneed
c.neededd.mayhaveneeded
19.Providingyou______theopportunitytogoabroad,whichcountrywouldyouwanttovisitfirst?
a.haveb.willhavec.hadd.havehad
20.Thebusinessofeachday,______sellinggoodsorshippingthem,wentquitesmoothly.
a.itbeingb.wasitc.itwasd.beit
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