浙江省嵊州市崇仁中学2026届高三上英语期末复习检测试题含解析

浙江省嵊州市崇仁中学2026届高三上英语期末复习检测试题请考生注意：1．请用2B铅笔将选择题答案涂填在答题纸相应位置上，请用0．5毫米及以上黑色字迹的钢笔或签字笔将主观题的答案写在答题纸相应的答题区内。写在试题卷、草稿纸上均无效。2．答题前，认真阅读答题纸上的《注意事项》，按规定答题。第一部分（共20小题，每小题1.5分，满分30分）1．ThatWasthefirsttimeshealoneathomeduringtheweekends，boredtodeath．A．hasleftB．hasbeenleftC．hadleftD．hadbeenleft2．________aboutthemanwearingsunglassesduringnightthathewasdeterminedtofollowhim.A．SocuriousthedetectivewasB．SocuriouswasthedetectiveC．HowcuriouswasthedetectiveD．Howcuriousthedetectivewas3．Scientistshavemanytheoriesabouthowtheuniverseintobeing.A．came B．wascoming C．hadcome D．wouldcome4．Howcomeeverykidtodayismeanttobeachampionforsomething_____weknoweverykidcan’tbeastar?A．incaseB．asifC．whenD．unless5．—Wouldyoumindmovingoveralittle?Ihavetopasshere.—________I’dliketohelp.A．Notintheslightest. B．Don’tmentionit.C．Nevermind. D．Atyourservice.6．—________It’sonlyaninterview!—Onlyaninterview?Onlyaninterview?WhatifIpanic?WhatifIsayasillywordbyaccident?A．Welldone!B．Comeon!C．Howcome?D．Nodoubt!7．IfIcanhelp,Idon’tlikeworkinglateintothenight.A．so B．that C．them D．it8．______caughtintherainunexpectedly,westillenjoyedthejourneyverymuch.A．When B．AsC．Unless D．Although9．AbookIreadlastyear,______nameIcan’tremember,changedmyideaabouttime.A．which B．thatC．whose D．what10．—Ken,________,butyourradioisgoingtooloud.—Oh,I’msorry.I’llturnitdownrightnow.A．Ihatetosayit B．Itdoesn’thurttoaskC．I’mreallytiredofit D．I’mcrazyaboutit11．Theshockingnewsmademerealize_____________terribleproblemswewouldface.A．that B．howC．why D．what12．Iamsothrilledtohavemyunderwaterphotos______intheNationalGeographicandonthecover!A．tobefeatured B．featured C．beingfeatured D．tofeature13．Thegovernmentplaced_____onthenumbersofforeigncarsthatcouldbeimported.A．limitations B．administrationC．requirements D．restrictions14．John______anNBAplayoffgameonTVnow.A．watchesB．watchedC．willwatchD．iswatching15．Theyoungviolinistisveryexcitedbecausetheconcertgivenbyhimhasneverbeen_____.A．successful B．moresuccessfulC．mostsuccessful D．themostsuccessful16．GeneralSecretary,XiJinping,stressedthatcross－straitcooperationwouldbestrengthened________thetwosidescouldagreetoopposeTaiwanindependence．A．unless B．evenifC．aslongas D．until17．________terrible,themedicinewasthrownawaybythechild.A．Tasted B．TastingC．Totaste D．Beingtasted18．They_______thebusinessdealinlessthananhour,afterwhichtheyhadagolfgame.A．wrappedup B．pickedupC．calledup D．tookup19．Withmoreforestsbeingdestroyed,hugequantitiesofgoodearth________eachyear.A．iswashingaway B．isbeingwashedawayC．arewashingaway D．arebeingwashedaway20．Moststudentsstudybecauseit’sunavoidable.________,therearestudentswhoactuallyenjoyit.A．Asaresult B．InadditionC．Inconclusion D．Bycontrast第二部分阅读理解（满分40分）阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。21．（6分）Inmyveryfirstjobwithsomearchaeologists,Iwasn’tdiggingobjectsoutoftheground,insteadIwasemployedasanartist,drawingwhattheyfound.However,Iwassoonmoreinterestedinthestoriesbehindtheobjectsthanindrawingthemandthat’showmycareerinarchaeologystarted.IstilldrawwhatIfindinmyworkasaspecialistontheSilkRoad,theoldtraderouterunningfromEgypttoMongolia,andIalsoworkonsomeunderwaterprojectstoo.Inarchaeology,myall-timeheroisanAmericancalledRaphaelPumpelly.IfirstheardabouthimwhenIwasastudentonatriptoTurkmenistan,acountryrightintheheartofAsia.Togetaroundthecountry,IhadtolearnRussiansothatIcouldspeaktothelocalpeople.WhenIgotthereIthought,“Wow!I’moneofthefirstAmericanshere!”ThenanoldmantoldmeaboutanAmericanarchaeologist,RaphaelPumpelly,whowastheredoingthesamethingover100yearsago.Archaeology’sinmyfamily.Mywife’sinthesameprofession,and,althoughourtwoboysaren’tinterestedinthefutureinarchaeologythemselves,we’vebeenonsomegreatdigstogetherandtheylovewhatwedobecausetheygettotravelwithus.Lastsummer,wetookthemtoLakeTiticacainSouthAmerica,inthehighareasoftheAndesmountainrange.MybestexperiencewaswhenIwasdiggingontheEgyptianRedSeacoast.There’sverylittlerainandit’ssodrythateverythingiskeptasitwas.Inanoldhouse,wheretheownerusedtostoregoodsfromtheshipsthatcamein,Ipickedupa700-year-oldmatinfrontofthehouseandthere,underit,afterallthattime,wasthehousekeywiththeowner’snamecarvedonit.Itfeltlikehecouldbeonhiswayhomeanyminute!AndIthought,“Hey,Idojustthat.Thisman’snotmuchdifferenttome!”1、WhileworkinginEgypt,whatdidthewriterfindsointeresting?A．Thatpeoplefromdifferentcenturiescanbesosimilar.B．Thefactthatthedoormatwasinsuchgoodcondition.C．Thewaythepeoplemanagedtoliveinsuchadryplace.D．Thattherehadbeensomuchtradeinthatarea.2、Whichentrywillthewriterprobablymakeinhisdiary?A．Turkmenistanisinteresting.I’mthefirstAmericantocomeherebutI’mgladthisismylasttripaway.B．Ihavebeendivingtodayandfoundsomeobjectsforanexhibition.I’vejustfinisheddrawingthemformyrecords.C．Iwishmychildrenweren’tmoreinterestedinarchaeologyandwouldnotworkhardintheopenliketheirparents.D．It’snearlydarkbutRaphael’sstillbusydigginginthatoldhouse.Hecanbeveryannoying.Hethinkshe’sthemostimportantpersonhere.3、Whatisthewriter’smainpurposeinwritingthetext?A．Todescribethelifeofanarchaeologistheadmires.B．Topersuadepeopletotakeuparchaeologyasacareer.C．Toexplainwhatheenjoysaboutbeinganarchaeologist.D．Toshowhowarchaeologistswork.22．（8分）PlanningavisittotheUK?Herewehelpwithwaystocutyourcosts.AVOIDBIGEVENTSBigsportingevents,concertsandexhibitionscanincreasethecostofaccommodationandmakeithardertofindaroom.AstandarddoubleroomattheThistleBrightonthefinalFridayoftheBrightonComedyFestival(19Oct.)cost￡169.15atB.Aweeklater,thesameroomcost￡118.15.Ifyoucanbeflexibleandwanttoknowdatestoavoid-oryou’relookingforabigeventtopassyourtime—checkoutsitessuchasWhatsonwhen.com,whichallowyoutosearchforeventsintheUKbycity,dateandcategory.STAYAWAYFROMTHESTATIONIftravelingtoyourdestinationbytrain,youmaywanttofindagoodbaseclosetothestation,butyoucouldenduppayingmoreforthesakeofconvenienceatthestartofyourholiday.Don’tbetoochoosyaboutthepartoftownyoustayin.Bookingtwomonthsinadvance,thecheapestroomatTravelodge’sCentralEustonhotelinLondonforSaturday22Septemberwas￡95.95.AroomjustatubejourneyawayatitsCoventGardenhotelwas￡75.75.AndatFarringdon,adoubleroomcostjust￡f62.95.LOOKAFTERYOURSELFReallycentralhotelsincitiessuchasLondon,EdinburghandCardiffcancostafortune,especiallyatweekendsandduringbigevents.Asanalternativeconsidercheckingintoaself-cateringflatwithitsownkitchen.Oftentheseflatsarehiddenawayonthetopfloorsofcitycentrebuildings.AgreatexampleisthehistoricO’NeillFlatonEdinburgh’sRoyalMile,availableforf420forfivedaysinlateSeptember,withroomforfouradults.1、AtW,youcan________.A．findaroomclosetothestationB．findaroomwhichcostslessC．knowhowtokilltimeD．knowwhenandwheretherewillbeevents2、“Farringdon”inParagraph5ismostprobably________.A．anidealholidaydestinationB．thenameofarailwaystationC．ahotelawayfromthetrainstationD．thetubelinetoCoventGarden3、ThepassageshowsthattheO’NeillFlat_________.A．liesonthegroundfloorB．providescookingfacilitiesfortouristsC．islocatedincentralLondonD．costsoverf100onaverageperdayinlateSeptember23．（8分）ACompetitiveSportOvertheyears,cheerleading(啦啦队)hastakentwoprimaryforms:game-timecheerleadingandcompetitivecheerleading.Game-timecheerleaders’maingoalistoentertainthecrowdandleadthemwithteamcheers,whichshouldnotbeconsideredasport.However,competitivecheerleadingismorethanaformofentertainment.Itisreallyacompetitivesport.Competitivecheerleadingincludeslotsofphysicalactivity.Themajorityoftheteamsrequireacertainleveloftumbling(翻腾运动)ability.It’saverycommonthingforgymnasts,soit’seasyforthemtogointocompetitivecheerleading.Usuallythesecheerleadersintegratelotsoftheirgymnasticsexperienceincludingtheirjumps,tumbling,andoverallenergy.Theyalsoperformliftsandthrows.Thisiswherethe“fliers”arethrownintheair,heldby“bases”indifferentpositionsthatrequirestrengthandworkingwithotherteammates.Competitivecheerleadingisalsoanactivitythatisgovernedbyrulesunderwhichawinnercanbedeclared.Itisawardedpointsfortechnique,creativityandsharpness.Usuallythemoredifficulttheactionis,thebetterthescoreis.That’swhycheerleadersaretryingtoexperiencegreatdifficultyintheirperformance.Besides,thereisalsoastrictruleoftime.Thewholeperformancehastobecompletedinlessthanthreeminutesandfifteenseconds,duringwhichthecheerleadersarerequiredtostaywithinacertainarea.Anyperformancebeyondthelimitoftimeisinvalid.Anotherreasonforthefactthatcompetitivecheerleadingisoneofthehardestsportsisthatithasmorereportedinjuries.Accordingtosomeresearch,competitivecheerleadingisthenumberonecauseofserioussportsinjuriestowomen.Emergencyroomvisitsforitarefivetimesthenumberthanforanyothersport,partiallybecausecheerleadersdon’tuseprotectiveequipment.Smilingcheerleadersarethrownintotheairandmovedownintothearmsoftheteammates,whichmayeasilycauseinjuries.Generally,theseinjuriesaffectallareasofthebody,includingwrists,shoulders,ankles,head,andneck.Therecanbenodoubtthatcompetitivecheerleadingisasportwithprofessionalskills.Hopefully,itwillappearintheOlympicssincecheerleadersarejustasathleticandphysicallyfitasthoseinvolvedinthemoreacceptedsports.Itshouldbenotedthatitisateamsportandeventhesmallestmistakemadebyoneteammatecanbringthescoreoftheentireteamdown.Sowithoutworkingtogethertoachievethegoal,firstplaceisoutofreach.1、Whatisthemainpurposeofcompetitivecheerleading?A．Tocompareskillsofparticipants.B．Tomaketheaudiencefeelamused.C．Toattractmorepeopletowatchevents.D．Tocheerupthecompetitorsonthecourt.2、Theunderlinedword“integrate”inParagraph2probablymeans“______”.A．examineB．combineC．identifyD．replace3、Wecanlearnfromthepassagethatcompetitivecheerleading______.A．lacksnecessaryguidelinestofollowB．enjoysgreaterpopularitythanothersportsC．requiresmoredesignedactionsthangymnasticsD．hasarelativelyhighrateofdamagetothebody4、Whichofthefollowingshowsthestructureofthepassage?I:IntroductionP:PointSp:Sub-point(次要点)C:ConclusionA．B．C．D．24．（8分）Whengoingthroughmajorlifechanges,likechangingcareers,IwouldchangethepeoplewithwhomIspentthemosttime.We’veallgonethroughperiodswhenthepeopleinourliveshavechanged—graduation,movingtoanewcity,gettinganewjob,joininganewclub,etc.Idon’tthinkIneedtoconvinceyoujusthowmuchinfluenceotherpeoplecanhaveoveryouridentity.Ifyou’veeverexperiencedamajorswitchinyourpeopleenvironment,thenyouknowthatyouchangeaswell.Mostpeopledon’tmakethesechoicesconsciouslythough.Youmightconsciouslydecidetospendmoretimewithacertainfriend,oryoumayasksomeoneoutonadatetobeginanewrelationship.Butfewpeoplechoosetheirexistingfriendshipsdeliberately.There’sno“gettingridofpeople”.Peoplearealwaysdroppingintoandoutofeachother’slives.Associationsgrowintofriendships,andfriendshipsfadeintoassociations.Youdon’tgetridofanyone.Thetruthisthatinordertomakeroomfornewpeopleandnewexperiences,youmayneedtoloosenupsomeofyourexistingconnections.Whataboutloyalty?Shouldn’tyoualwaysbeloyaltoyourfriends?Onceyouhaveaclosefriend,eveniftheirinfluenceonyouisslightlyharmful,shouldn’tyoustickbythem?Loyaltytoafriendsometimesmeanshavingtoletgo.Itmeansbeingloyaltotheirhighestandbestaswell.Ifsomeoneisdestroyinghishealthbysmoking,forexample,youaren’tshowingloyaltybysmokingrightalongwithhim.Trueloyallysometimesrequiresthatyoubreakdamagingconnections,getyourselfbackonsolidground,andthendecidewhatyoucanreallydotohelpyourfriend.Itcantakealotofcouragetotellsomeone,“I’msorry,butIcan’thaveyouinmylifeanymore."Buteventhoughthismightseemlikeaselfishactattimes,it’softenthebestthingfortheotherpersontoo.Ifarelationshipisholdingyoubackinsomeway,understandthatitisalsohurtingtheotherperson.Forexample,ifyouworkforaviolentboss,youracceptanceofthatsituationisconsideredtobesilentapproval,encouragingyourbosstocontinuetobehaveviolently.1、Whenexperiencingmajorlifechanges,peoplemay________.A．joinanewsocialcommunityB．influencetheirfriendsaroundC．choosetheirfriendshipspurposelyD．havetheirpeopleenvironmentchanged2、WhatcanbeconcludedfromParagraph3inthepassage?A．Everyonehasatleastonefriend.B．Friendshipstillexiststhoughthere’slessconnection.C．Itisunnecessarytomakenewfriends.D．Yououghttotreatyouroldandnewfriendequally.3、Whatistheauthor’sopinionontheloyaltytofriends?A．Neverbetrayyourclosefriendswhateverhappens.B．Correcttheirmistakeswhileyouguardtheirgoodness.C．Stickbyyourfriendseventhoughtheydoharmloyou.D．Breakupwithyourfriendsimmediatelyiftheysmoke.4、Howshouldwebehavewhenemployedbyaviolentboss?A．Weshouldacceptwhatwearetoldtodo.B．Weshouldstaysilentandbeinfavorofit.C．Weshouldbravelydisobeyhimifheiswrong.D．Weshouldgiveourbosscouragetocontinue.25．（10分）PeoplefromEastAsiatendtohavemoredifficultythanthosefromEuropeindistinguishingfacialexpressions—andanewreportpublishedonlineinCurrentBiologyexplainswhy.RachaelJack,UniversityofGlasgowresearcher,saidthatratherthanscanningevenly(均匀的)acrossafaceasWesternersdo,Easternersfixtheirattentionontheeyes."WeshowthatEasternersandWesternerslookatdifferentfacefeaturestoreadfacialexpressions,"Jacksaid."Westernerslookattheeyesandthemouthinequalmeasure,whereasEasternersfavortheeyesandneglect(忽略)themouth."AccordingtoJackandhercolleagues,thediscoveryshowsthathumancommunicationofemotionismorecomplexthanpreviouslybelieved.Asaresult,facialexpressionsthathadbeenconsidereduniversallyrecognizablecannotbeusedtoreliablyconveyemotionincross-culturalsituations.Theresearchersstudiedculturaldifferencesintherecognitionoffacialexpressionsbyrecordingtheeyemovementsof13WesternCaucasianand13EastAsianpeoplewhiletheyobservedpicturesof.expressivefacesandputthemintocategories:happy,sad,surprised,fearful,disgusted,angry,orneutral.Theycomparedhowaccuratelyparticipantsreadthosefacialexpressionsusingtheirparticulareyemovementstrategies.ItturnedoutthatEasternersfocusedmuchgreaterattentionontheeyesandmadesignificantlymoreerrorsthandidWesterners."Theculturaldifferenceineyemovementsthat____showisprobablyareflectionofculturaldifferenceinfacialexpressions,"Jacksaid."OurdatasuggestthatwhereasWesternersusethewholefacetoconveyemotion,Easternersusetheeyesmoreandmouthless."Inshort,thedatashowthatfacialexpressionsarenotuniversalsignalsofhumanemotion.Fromhereon,examininghowculturalfactorshavediversifiedthesebasicsocialskillswillhelpourunderstandingofhumanemotion.Otherwise,whenitcomestocommunicatingemotionsacrosscultures,EasternersandWesternerswillfindthemselveslostintranslation.1、ThediscoveryshowsthatWesterners.A．payequalattentiontotheeyesandthemouthB．considerfacialexpressionsuniversallyreliableC．observetheeyesandthemouthindifferentwaysD．havemoredifficultyinrecognizingfacialexpressions2、Whatwerethepeopleaskedtodointhestudy?A．Tomakeafaceateachother. B．Togettheirfacesimpressive.C．Toclassifysomefacepictures. D．Toobservetheresearchers'faces.3、Whatdoestheunderlinedword"they"inParagraph6referto?A．Theparticipantsinthestudy.B．Theresearchersofthestudy.C．Theerrorsmadeduringthestudy.D．Thedatacollectedfromthestudy.4、IncomparisonwithWesterners,Easternersarelikelyto.A．dotranslationmoresuccessfullyB．studythemouthmorefrequentlyC．examinetheeyesmoreattentivelyD．readfacialexpressionsmorecorrectly5、Whatcanbethebesttitleforthepassage?A．TheEyeastheWindowtotheSoulB．CulturalDifferencesinReadingEmotionsC．EffectiveMethodstoDevelopSocialSkillsD．HowtoIncreaseCross-culturalUnderstanding第三部分语言知识运用（共两节）第一节（每小题1.5分，满分30分）阅读下面短文，从短文后各题所给的A、B、C和D四个选项中，选出可以填入空白处的最佳选项．26．（30分）FlowersforMissBensonMissBensonwasthekindest,sweetest,mostbeautifulpersonontheearthinmymind.Shewasmysecond-grade1.Earlyintheterm,IstartedaskingmymothertoputanextraappleinmylunchforMissBenson.2Ineverquiteworkedupthecouragetohandmygifttoher3.Eachdayitfounditswayunobservedtothecornerofherdesk.Andeachdaytheresponsewasthesame:MissBensonwouldcomeinandsitdown.“Goodmorning,children.Why,hownice!”Shewouldpickupthe4oftheday,andthenlookaroundtheroom.“What5littleboyorgirlbroughtmethis?”Noone6thehonor,leastofallme.Ikeptmyheaddown,lookingatmydesk.“CanitbethatIhaveasecretadmirer?”shewouldask.Iwouldfeelthe7risinginmyface.Iwascertainthateveryonewaslookingatme,andIwouldsighwith8whenMissBensonstartedthelessonafterputtingthefruitaway.Onefallmorning,theclasswasboilingwith9.Aswassaid,thenextday,Friday,wasMissBenson’sbirthday.Everyonewantedtogetherapresent.Myheartgaveajump;atlastIcouldgivehersomething10.Thatafternoonwasspentcombingthefieldsforwildflowers.InthemorningIhungbackasothers11theirgifts.FinallyIwenttothedeskandgavetheflowerstoMissBenson.Myrewardwasasmileandapatonthehead.ThenextMonday,MissBensondidn’t12.Lateron,Iwasaskedtogototheprincipal'soffice.He,clearlyandslowly,toldmethatbecauseofthepoison13Igaveher,MissBensonwasinhospital.I14allthewayhomebecauseofthetragedytomylovingteacher.IbeggedmymothertotakemetovisitMissBenson.MissBensonwassittingupinbedwhenwearrived.Her15wascoveredwithbandages.Onlyoneeyewasshowing.“Ididn’tknowtheywerepoisonflowers,”Iburstout.“Ididn’t16tomakeyousick.Ionlywantedtogiveyousomething.....”Istoppedtalkingandswallowedhard.MissBenson17mewiththeeye.“Youwantedtogivemesomething18,didn’tyou,Paul?”Inodded.“Allthose19werefromyou,weren’tthey?”AgainInodded.“I’lltellyouagreatbigsecret,Paul,”shecontinued,“WhenIammarried,ifIhaveason,Iwouldlikehimtogrowupjust20you.”Iwasn’tcertainthatIsawtearsinhereyeasMotherledmeoutoftheroom.1、A．studentB．classmateC．fellowD．teacher2、A．SoB．AndC．ButD．For3、A．secretlyB．directlyC．gentlyD．beautifully4、A．offeringB．huntingC．remainingD．catching5、A．usefulB．forgetfulC．shamefulD．thoughtful6、A．claimedB．sharedC．mindedD．refused7、A．coldB．redC．darkD．proud8、A．shameB．anxietyC．reliefD．anger9、A．disappointmentB．excitementC．embarrassmentD．amusement10、A．openlyB．quietlyC．casuallyD．safely11、A．boughtB．fetchedC．broughtD．presented12、A．awakeB．agreeC．appearD．answer13、A．flowersB．leavesC．plantsD．fruit14、A．laughedB．sangC．shoutedD．sobbed15、A．legB．armC．faceD．hair16、A．manageB．meanC．failD．hesitate17、A．blamedB．scoldedC．punishedD．studied18、A．simpleB．specialC．awfulD．useful19、A．applesB．orangesC．bananasD．pears20、A．besideB．forC．likeD．by第二节（每小题1.5分，满分15分）阅读下面材料，在空白处填入1个适当的单词或括号内单词的正确形式。27．（15分）Thereisadiseasesweepingtheworldtodaythatiskillingfarmorepeoplethananyother,AIDSorSARS1．(include).Thatdiseaseisobesity.TheWHOhasstatedthatofthe56.5million2．(die)peryeararoundtheworld,over50percentofthesearecausedbydiseases3．(close)associatedwithunhealthydietandlackofexerciseand4．manyofthesedeathscouldbeprevented.TheWHOannounced,in2014,aplan5．(fight)obesityandinvitedgovernmentstoencourageitscitizenstoadopta6．(sense)dietandtotakeupsomeexercise.Aspartoftheirplan,theWHOaskedgovernmentstoconsidertherolefoodadvertisingplays7．encouragingpeopletoeatunhealthyfood.Oneareaofconcernformanycountriesistheadvertisingofunhealthyfoodduringchildren'stelevisionprograms.InAustralia，whichhasthehighestnumberoffoodadvertisementsinchildren’stelevisionintheworld,thereare8．averageof12foodadsperhour.WhileinSwedenandAustria9．therearestrictlawsaboutadvertisingduringchildren'sprograms,thereisonlyonefoodperhour.InSweden,andQuebecinCanada,there10．(be)nogreatdifferenceinthenumberofobesechildrensincethegovernmentbannedfoodadsinchildren'stelevision.第四部分写作（共两节）第一节短文改错（满分10分）28．（10分）假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。增加:在缺词处加一个漏字符号(∧)，并在其下面写出该加的词。删除:把多余的词用斜线(＼)划掉。修改:在错的词下画一横线，并在该词下面写出修改后的词。注意：1、每处错误及其修改均仅限一词；2、只允许修改10处，多者(从第11处起)不计分。DearLiHua，Inyourlastemail，youmentionedyoufeltfrustratingatyoursmallvocabulary、Now，I’dliketos