冠詞專項練習(xí)100道

1.Iknew______JohnLennon,butnot____famousone.A./,aB.a,theC./,theD.the,a解釋：IknewaJohnLennon,表示我認(rèn)識一個John，人名表示某一個用不定冠詞；thefamousone指的是大家熟悉的那個。答案：B2.Foralongtimetheywalkedwithoutsaying________word.Jimwasthefirsttobreak________silence.A.the;aB.a;theC.a;不填D.the;不填解釋：word是單數(shù)名詞用不定冠詞；前文的withoutsayingaword已經(jīng)表示silence是大家熟悉的。答案：B3.Ifyoubuymorethanten,theyknock20penceoff________.A.apriceB.priceC.thepriceD.prices解釋：price是之前知道的價格答案：C4.Thesignreads“Incaseof________fire,breaktheglassandpress________redbutton.”A./;aB./;theC.the;theD.a;a解釋：fire是抽象名詞，用零冠詞；redbutton前有thesignreads，表示熟悉。答案：B5.Manylifestylepatternsdosuch________greatharmtohealththattheyactuallyspeedup________weakeningofthehumanbody.

A．a(chǎn)；/B．/；theC．a(chǎn)；theD．/；/解釋：doharmto是固定詞組；這里的weakening是動名詞，后面有ofthehumanbody修飾，表示特指。答案：B6.—Whatdoyouthinkabout________dressintheshopwindow

—Oh，it’sbeautiful.YoumaygiveittoLindaas________birthdaypresent.

A．a(chǎn)；aB．the；aC．a(chǎn)；theD．the；the解釋：下文有g(shù)iveitto,表示dress雙方都熟悉;present是單數(shù)名詞，用不定冠詞。答案：B7.Duringthecamptrip，childrenwerefascinatedby________wondersof________nature.

A．/；/B．/；theC．the；/D．the；the解釋：wonders已經(jīng)在camptrip中被孩子們熟悉；nature，society，Space前不加the。答案：C8.Itisclearthat________littlemoneytheinventionwillbringhimcanhardlysupportsolarge________company.

A．/；theB．a(chǎn)；theC．a(chǎn)；/D．the；a解釋：后文的bringhimcanhardly特指這筆money；so+形容詞+a/an+可數(shù)名詞答案：D9.________on-goingdivisionbetweenEnglish-speakingCanadiansandFrench-speakingCanadiansis________majorconcernofthecountry.A.The;不填B.The;aC.An;theD.An;不填解釋：on-goingdivision后有between...限制表示特指；concern是單數(shù)名詞，這里用不定冠詞。答案：B10.Themostimportantthingaboutcottoninhistoryis________partthatitplayedin________IndustrialRevolution.A.不填;不填B.the;不填C.the;theD.a;the解釋：part后面有that補(bǔ)充表示特指；IndustrialRevolution是專有名詞，指工業(yè)革命，專有名詞前要加定冠詞。答案：C11.Thechairmanwillbepleasedat________scenethateverythingisin________place.

A．a(chǎn)；aB．the；theC．the；/D．/；the解釋：scene有下文that補(bǔ)充，表是特指；inplace是固定搭配，表示順利。答案：C12.Ifweexpect________muchcleanerworld，weshouldattract________world’sattentiontoprotectingtheworld.

A．a(chǎn)；aB．a(chǎn)；/C．a(chǎn)；theD．the；/解釋：這里world是指世界的意思，是不可數(shù)名詞，前面加了cleaner形容詞，要用不定冠詞；attractattention是固定搭配，world’sattention中的world為不可數(shù)名詞，要用零冠詞。答案：C13.Weworktogethertoachieveourcommonpurpose：________worldthatissafer，cleanerandhealthierthan________onewefound.

A．the；theB．a(chǎn)；/C．a(chǎn)；theD．the；/解釋：這里world是指地球的意思，是可數(shù)名詞，用不定冠詞；onewefound特指我們found的world，用定冠詞。答案：C14.Papermoneywasin________useinChinawhenMarcoPolovisitedthecountryin________thirteenthcentury.A.the;不填B.the;theC.不填;theD.不填;不填解釋：inuse是固定搭配；thirteenth是序數(shù)詞，前面加定冠詞。答案：C15.Thisareaexperienced________heaviestrainfallin________monthofMay.

A．/；aB．a(chǎn)；theC．the；theD．the；a解釋：heaviest是最高級，前面加定冠詞；month前要加定冠詞，但是具體的月份就要用零冠詞，比如inJanuary,inFebruary,inMarch,inApril。答案：C16.On________newstoday,therewere________reportsofheavysnowinthatarea.A.the;theB.the;不填C.不填;不填D.不填;the解釋：news后有today修飾，表示特指；reports是復(fù)數(shù)名詞，表示泛指，加零冠詞。答案：B17.________WorldExpoisregardedastheOlympicGamesoftheeconomy，scienceandtechnology，________expertsaid.

A．A；anB．The；anC．The；aD．A；the解釋：WorldExpo是專有名詞，是世界博覽會的意思，用定冠詞；這里的expert是可數(shù)名詞，用定冠詞，并且第一個音素為元音，所以用an。答案：B18.Asisknowntoall.____People’sRepublicofChina..A.The;B.不填解釋：當(dāng)中國翻譯為china時，前面用零冠詞，用普通名詞構(gòu)成的專有名詞前加the,比如thePeole’sRepublicofChina.美國，翻譯為USA時，前面用零冠詞，否則用theUnitedStateofAmerica.答案：A19.Whenheleft________college,hegotajobas________reporterinanewspaperoffice.A.不填;aB.不填;theC.a;theD.the;the解釋：Leftcollege是固定搭配，表示畢業(yè)；reporter是可數(shù)名詞，加不定冠詞。答案：A20.Whenyoucomehereforyourholidaynexttime,don’tgoto________hotel;Icanfindyou________bedinmyflat.A.the;aB.the;不填C.a;theD.a;不填解釋：Gohome兩個字，gotoschool三個字，其他都是四個字；bed是可數(shù)名詞，用不定冠詞。答案：A21.Thereareover58,000rockyobjectsinspace，about900ofwhichcouldfalldownonto________earth.

A．the；theB．/；theC．the；/D．a(chǎn)；the解釋：space,nature,society前不用the；earth，moon等星球前面用the，火星，金星等星類不用the。答案：B22.Whenyoufinishreadingthisbook,youwillhave________betterunderstandingof________life.A.a,theB.the,aC./,theD.a,/解釋：understanding是抽象名詞，前面有better修飾，用不定冠詞；這里life是指人生，是抽象名詞，前后無修飾，用零冠詞。答案：D23.I’dlike________informationaboutthemanagementofyourhotel,please.—Well,youcouldhave________wordwiththemanager.Hemightbehelpful.A.some,aB.an,someC.some,someD.an,a解釋：information是不可數(shù)名詞；haveawordwith是固定搭配。答案：A24.Whilehewasinvestigatingwaystoimprovethetelescope,Newtonmade________discoverywhichcompletelychanged________man’sunderstandingofcolour.A.a…不填B.a…theC.不填…theD.the…a解釋：makeadiscovery是固定搭配；這里man指全人類，加the就變成了那個人。答案：A25.Manypeopleagreethat________knowledgeofEnglishisamustin________internationaltradetoday.A.a;/B.the;anC.the;theD./;the解釋：aknowledgeof是固定搭配；internationaltrade不是專有名詞，trade是不可數(shù)名詞，用零冠詞。答案：A26.Thedriverwasat________losswhen________wordcamethathewasforbiddentodriveforspeeding.

A．a(chǎn)；theB．/；/C．the；theD．a(chǎn)；/解釋：ataloss是固定搭配；word后文有that修飾，表示特指。答案：A27.Tomowns________largercollectionof________booksthananyotherstudentinourclass.A.the;不填B.a;不填C.a;theD.不填;the解釋：collection是可數(shù)名詞，用不定冠詞；books是復(fù)數(shù)名詞，前面用零冠詞。答案：B28.Mostanimalshavelittleconnectionwith________animalsof________differentkindunlesstheykillthemforfood.A.the;aB.不填;aC.the;theD.不填;the解釋：animals是復(fù)數(shù)名詞，前面用零冠詞；akindof是固定搭配。答案：B29.Thevisitorsherearegreatlyimpressedbythefactthat________peoplefromallwalksoflifeareworkinghardfor________newJiangsu.

A．/；aB．/；theC．the；aD．the；the解釋：people是不可數(shù)名詞，前面用零冠詞，Jiangsu本是抽象名詞，要用零冠詞，但是前面有new形容詞修飾，要加冠詞，因不是特指，所以用不定冠詞。答案：A30.WashingmachinesmadebyChinahavewon________worldwideattentionandHaierhasbecome______popularname.

A．a(chǎn)；theB．/；aC．/；theD．the；a解釋：winone’sattention是固定搭配；name是可數(shù)名詞，前面用不定冠詞。答案：B31.—Stayabitlonger，please.It’sbeensuch________funhavingyouhere.

—Thankyou，butI’vegot________earlystarttomorrowmorning.

A．/；theB．a(chǎn)；anC．/；anD．the；an解釋：fun是不可數(shù)名詞，用零冠詞；getanearlystart是固定搭配，提早出發(fā)。答案：C32.Dr.PeterSpence,_____headmasteroftheschool,told...A.不填；B.The;C.A解釋：職位、頭銜前面用零冠詞。答案：A33.TheWilsonslivein________A-shapedhousenearthecoast.Itis________17thcenturycottage.A.the,/B.an,theC./,theD.an,a解釋：A-shapedhouse后面有nearthecoast特指，可以用the，也可以用an；cottage是可數(shù)名詞，要用不定冠詞。答案：D34.—Haveyouseen________penIleftitherethismorning.—Isit________blackoneIthinkIsawitsomewhere.a;theB.the;theC.the;aD.a;a解釋：pen是可數(shù)名詞，用不定冠詞；是不是blackone不確定，不能用定冠詞，也要用不定冠詞。答案：D35.Jumpingoutof________airplaneattenthousandfeetisquite________excitingexperience.A.不填,theB.不填,anC.an,anD.the,the解釋：airplane是可數(shù)名詞，用不定冠詞；這里Experience是指經(jīng)歷，是可數(shù)名詞，也要用不定冠詞，exciting第一音素是元音，用an。答案：C36.Firstimpressionsarethemostlasting.Afterall，youneverget________secondchancetomake________firstimpression.

A．a(chǎn)；the??B．the；theC．a(chǎn)；a??D．the；a解釋：secondchance是名詞，不是序數(shù)，用不定冠詞；Firstimpression也是名詞，用不定冠詞。答案：C37.Indiaattainedindependencein1947,afterlongstruggle.A.不填;a B.the;aC.an;不填 D.an;the解釋：independence是抽象名詞，用零冠詞；struggle也是抽象名詞，但前面有l(wèi)ong修飾，要用不定冠詞。答案:A38.Itwascoldwinternightandthemoonwasshiningbrightlyacrossnightsky.A./;a B.a;theC.the;a D.the;/解釋：night是抽象名詞，前面有coldwinter修飾，要用不定冠詞；sky是獨一無二的，前面要加定冠詞。答案:B39.MarcoPoloissaidtohavesailedonPacificOceanonhiswaytoJavainthirteenthcentury.A.the;a B.a;不填C.不填;the D.the;the解釋：PacificOcean是專有名詞，前面加定冠詞；thirteenthcentury是序數(shù)，前面加定冠詞。答案:D40.Theparentswereshockedbynewsthattheirsonneededoperationonhisknee.A.a;/ B.the;/C.the;an D.a;an解釋：news是專有名詞，前面要加定冠詞；operation是可數(shù)名詞，要加不定冠詞。答案:C41.Animalsareobviouslylowerformoflifethanman.?A.a;/ B.the;theC.a;the D./;/解釋：aformof是固定搭配；man前面加the表示人類。答案:A42.The“ChineseDream”isdreamtoimprovepeople’swell-beinganddreamofharmony,peaceanddevelopment.?A.the;a B.a;a C.a;the D.the;the解釋：dream是可數(shù)名詞，前面加不定冠詞。答案:B43.Sarahlookedatfinishedpaintingwithsatisfaction.A.不填;a B.a;theC.the;不填 D.the;a解釋：painting是可數(shù)名詞，前面有finished修飾，表示特指，用定冠詞；satisfaction是不可數(shù)名詞，要加零冠詞。答案:C44.Carlisstudyingfoodscienceatcollegeandhopestoopenupmeatprocessingfactoryofhisownoneday.A./;a B./;the C.the;a D.the;the解釋：foodscience是一門學(xué)科，學(xué)科球類三餐飯前用零冠詞；factory是可數(shù)名詞，用不定冠詞。答案:A45.Thedevelopmentofindustryhasbeengradualprocessthroughouthumanexistence,fromstonetoolstomoderntechnology.A.不填;the B.the;a C.a;不填 D.a;a解釋：process是可數(shù)名詞，用不定冠詞；existence是不可數(shù)名詞，用零冠詞。答案:C46.WearesaidtobelivinginInformationAge,timeofnewdiscoveriesandgreatchanges.?A.an;the B.不填;theC.不填;a D.the;a解釋：informationAge是專有名詞，用定冠詞；atimeof是固定詞組，要牢記。答案:D47.Iwokeupwithbadheadache,yetbyeveningthepainhadgone.?A.the;the B.the;anC.a;the D.a;an解釋：haveaheadache，getaheadache是固定詞組；evening特指昨天晚上，用定冠詞。答案:C48.Itisgenerallyacceptedthatboymustlearntostandupandfightlikeman.?A.a;a B.a;the C.the;the D.a;/解釋：boy和man都是可數(shù)名詞，文中表示泛指，用不定冠詞。答案：A49.Takeyourtime—it’sjustshortdistancefromheretorestaurant.(2011山東,21)?A.不填;the B.a;the C.the;a D.不填;a解釋：distance是不可數(shù)名詞，但前面偶short修飾，用不定冠詞；restaurant有前面fromhereto表示特指。答案：B50.Inmostcountries,auniversitydegreecangiveyouflyingstartinlife.(2010四川,2)?A.the;a B.the;不填 C.不填;不填 D.不填;a解釋：countries已經(jīng)是復(fù)數(shù)形式，most表示大部分，不用定冠詞，要用零冠詞；start是可數(shù)名詞，用不定冠詞。答案：D51.Everythingcomeswithprice;thereisnosuchthingasafreelunchintheworld.?A.a;a B.the;/ C.the;a D.a;/解釋：price是可數(shù)名詞，用不定冠詞；nosuchthing是固定搭配，等于notsuchathing。答案：D52.Whatpitythatyoucouldn’tbetheretoreceiveprize!?A.a;a B.the;aC.a;the D.the;the解釋：whatapity是固定搭配；prize是雙方都熟悉的，用定冠詞。答案：C53.Beingabletoafforddrinkwouldbecomfortinthosetoughtimes.?A.the;the B.a;aC.a;不填 D.不填;a解釋：drink作為飲料時是可數(shù)名詞，用不定冠詞；comfort后省略了具體的名詞，前面用不定冠詞。答案：B54.Hemissedgoldinthehighjump,butwillgetsecondchanceinthelongjump.?A.the;the B.不填;aC.the;a D.a;不填解釋：gold后有inthehighjump特指，用定冠詞；secondchance整體作為名詞，用不定冠詞。答案：C55.Dr.PeterSpence,headmasteroftheschool,toldus,“fifthofpupilsheregoontostudyatOxfordandCambridge.”?A./;AB./;TheC.the;The D.a;A解釋：headmaster是頭銜，用零冠詞；afifth表示五分之一。答案：A56.Peopledeveloppreferenceforaparticularstyleoflearningatearlyageandthesepreferencesaffectlearning.?A.a;an B.a;/C./;the D.the;an解釋：developapreferencefor是固定搭配；atanearlyage也是固定搭配。答案：A57.SamhasbeenappointedmanageroftheengineeringdepartmenttotakeplaceofGeorge.A./;/ B.the;/ C.the;the D./;the解釋：manager是頭銜，又有后面oftheengineeringdepartment作同位語，前面用零冠詞；taketheplaceof是固定搭配。答案：D58.—It’ssaidJohnwillbeinajobpayingover$60,000year.?—Right,hewillalsogetpaidbyweek.A.the;the B.a;the C.the;a D.a;a解釋：ayear表示每年；bytheweek是固定搭配，表示以周計算。答案：B59.Weallsignedwithreliefwhenplanefinallylandedsafely.A.a;/ B./;the C.a;a D.a;the解釋：relief是不可數(shù)名詞，前面用零冠詞；文中的plane是雙方都知道的，用定冠詞。答案：B60.LinDan’srecentbook,whichisbasedonhisexperienceasOlympicbadmintongoldwinner,becamebestsellerinChina.A./;a B.an;the C./;the D.an;a解釋：winner是可數(shù)名詞，用不定冠詞；bestseller也是可數(shù)名詞，用不定冠詞。答案：D61.AsbirthplaceofHuaxiacivilization,Xi’aniscitywithalonghistoryandabundantculturalrelics.?A.the;a B.a;a C./;a D.the;/解釋：birthplace后面有huaxiacivilization修飾，前面用定冠詞；city是可數(shù)名詞，前面用不定冠詞。答案：A62foodanddrugchannelwithclearexplanations,isverypopularwebsite.?A.a;a B.a;the C.the;/ D./;a解釋：channel和website都可數(shù)名詞，用不定冠詞。答案：A63.—Doyouthinkanadvertisementishelpwhenyoulookforacollege?—Well,italldepends.Anyway,itgivesmemoreofchance.A.a;a B.the;the C./;the D.a;the解釋：help作為名詞是可數(shù)名詞；chance是可數(shù)名詞答案：A64.InChina,pressuretofindjobscausessomestudentsinthecountrysidetodroptheirdreamsofgoingtocollege.A./;the B.a;the C.the;/ D./;/解釋：pressure后面有find…特指，用定冠詞；jobs是復(fù)數(shù)名詞，用零冠詞。答案：C65.IhadfeelingofhappinesswhenIheardthathehadwonfirstprizeinthecontest.?A.a;the B.the;/ C.the;a D.a;a解釋：feeling是可數(shù)名詞，前面用不定冠詞；prize是可數(shù)名詞，前面有first修飾，表示特指，用定冠詞。答案：A66.ThenextmorningwewenttolectureaboutPompei,whichwasfoundedin8thcenturyBC.?A.the;the B.a;/ C./;the D.a;the解釋：lecture是可數(shù)名詞，用不定冠詞；8th是序數(shù)，用定冠詞。答案：D67.ItcameasshockthatfirebrokeoutinShanghaiyesterday,killingatleast5people.?A.a;a B.a;/ C./;a D.the;the解釋：本文的shock指令人震驚的事，是可數(shù)名詞，用不定冠詞；afire表示一場大火。答案：A68.Theoperationissuccessandthepatientisnowoutofdanger.A.a;the B.a;/ C./;the D./;/解釋：本文success是指具體成功的人或事物，是可數(shù)名詞，用不定冠詞；outofdanger是固定搭配。答案：B69.LocalpeoplesaidIsraelitroopswereseenbeforedawnintownofBeitLahiya,northofGazacity.?A./;/ B.a;the C.the;the D.the;/解釋：town后面有beitlahiya修飾，特指，用定冠詞；northof前面用零冠詞，記牢。答案：D70.—Mom,I’msorrytotellyouIfailedmathstest.?—Don’tloseheart.But,givensecondchance,youaresupposedtopass.A.the;the B.the;a C.a;a D.a;the解釋：maths指雙方都知道的考試，用定冠詞，本題牢記；secondchance整體是名詞，用不定冠詞。答案：B71.Mrs.Chenispaper-cuttingexpert,whomIinterviewedformyarticleonChineseArt.?A.a;the B.an;/ C.a;/ D.an;the解釋：expert是可數(shù)名詞，前面用不定冠詞；chineseart是學(xué)科，用零冠詞。答案：C72.—WhendidyoulastseeShelly—OnSundayoflastDecemberatcelebrationofher40thweddinganniversary.?A.不填;the B.a;不填 C.the;a D.a;the解釋：Sunday后面有oflastDecember修飾，用不定冠詞；celebration后有40thwedding修飾，用定冠詞。答案：D73.Delahadmadeuphismindtogiveitup,butonsecondthought,hedeterminedtotrythirdtime.?A./;a B./;/ C.a;a D.the;a解釋：secondthought是固定搭配，用零冠詞；thirdtime整體是名詞，用不定冠詞。答案：A74.ItisreportedthataudienceofmillionswatchedweddingbetweenPrinceWilliamandKateonTVthatday.?A.a;an B.an;the C.the;the D.the;an解釋：anaudienceof是固定搭配；wedding后有between修飾，用定冠詞。答案：B75.Manypeopleinwesterncountriesgotochurchon,asdosomeChinese.?A.∕;aSunday B.the;SundayC.∕;Sundays D.the;Sundays解釋：gotochurch為固定短語，意為做禮拜；onSundays表示所有星期天。答案：C76.ThereisnodoubtthattheDiaoyuIslandsarepartofChinaandwhatsomeJapanesehavedonerecentlyisactuallyoffenceagainstChinesepeople.A.a;/ B.a;theC.the;/ D./;an解釋：partofsth是固定搭配；offence是可數(shù)名詞，用不定冠詞。答案：D77.Jackleftmessageforme,sayinghewasintrouble.A.a;the B.a;/ C./;/ D.the;a解釋：message是可數(shù)名詞，用不定冠詞；introuble是固定搭配。答案：B78.Intheearlymorningallofusstoodatthetopofthemountaintoeastofthecity,watchingburningsunrising.?A.the;a B./;a C.the;the D.the;/解釋：east是方位名詞，前面加定冠詞。Sunrising是不可數(shù)名詞，前面有burning修飾，用不定冠詞。答案：A79.Letussupposeyouareinpositionofparent.Wouldyouallowyourchildtodosuchathing?A.a;a B.a;the C.the;a D.the;the解釋：inthepositionof是固定搭配；parent是可數(shù)名詞，用不定冠詞。答案：C80.—Wouldyoumindgivingyouradviceonhowtoimproveourbusinessmanagement—Ifyoumakemostofthemodernequipment,therewillberiseinproduction.?A./;/ B.the;a C./;a D.the;/解釋：makethemostof是固定搭配，表示充分利用。本文中rise是可數(shù)名詞，用不定冠詞。答案：B81.Historically,mainmaterialformakingtableshasbeenwood,butmetalandstonehavealsobeenused.A.the;/ B./;/ C.the;the D./;the解釋：mainmaterial后面有formaking修飾，表示特指，用定冠詞；metalandstone作為抽象名詞，用零冠詞。答案：A82.WhatlessonsChinacandrawfromglobalfinancialcrisishasbecomehottopicamongusstudents.A.the;a B./;a C.a;the D./;the解釋：globalfinancialcrisis是專有名詞，用定冠詞；topic是可數(shù)名詞，用不定冠詞。答案：A83.Inthepastthreedecades,significantadvancehasbeenmadeinmodernagriculture.?A.a;/ B.the;a C./;the D.a;a解釋：makeasignificantadvance是固定搭配；agriculture是不可數(shù)名詞，不用冠詞，要牢記。答案：A84.Assistancedogsaretrainedtohelpdisabledtolivemoreindependentlife.?A./;a B.a;the C.the;a D.the;the解釋：thedisabled是固定搭配，表示一類人；livea...life是固定搭配。答案：C85.successofZhuZhiwen’ssinginghasbeengreathonourtohishometown.?A.The;a B.The;an C./;the D.The;/解釋：success后有ZhuZhiwen’ssinging修飾，用定冠詞；honour是不可數(shù)名詞，但用不定冠詞表示具體的事。答案：A86.HavingdinnertogetheronNewYear’sEvehasalwaysbeenbigdealformyfamilyanditgivesuspleasure.?A.the;/ B.a;the C.a;a D.a;/解釋：abigdeal是固定搭配，表示重要的事；本文pleasure為抽象名詞，用不定冠詞。答案：D87.Awarded2012NobelPrizeinLiterature,MoYan,productivecontemporaryChinesewriter,haspublisheddozensofshortstoriesrelatedtothecountryside.?A.a;a B.the;a C./;a D.a;the解釋：NobelPrize是專有名詞，用定冠詞；writer是可數(shù)名詞，前用不定冠詞。答案：B88.China’syouthstoppedalistofcalculatingabilities,butrankedlastonimaginationand5thfrombottomforcreativity,accordingtoaneducationsurveyof21countriesandregions.?A.the;the B.an;the C./;the D./;a解釋：imagination是抽象不可數(shù)名詞，用零冠詞；bottom后有for...修飾，用定冠詞。答案：C89.TheearthquaketookplaceonFridayafternooninMarchanddidgreatdamagetothecountry.A./;/ B.a;a C.a;/ D.the;a解釋：Friday后有march在，要用不定冠詞，表示三月份某個周五；dodamagetosb是固定搭配。答案：C90