2026年上半年全国英语等级考试（PETS）四级全真模拟试题(山东泰安)

2026年上半年全国英语等级考试（PETS）四级全真模拟试题(山东泰安)SectionIListeningComprehensionPartADirections:Youwillhearfiveshortconversationsbetweentwospeakers.Attheendofeachconversation,aquestionwillbeaskedaboutwhatwassaid.Boththeconversationandthequestionwillbespokenonlyonce.Aftereachquestiontherewillbeapause.Duringthepause,youmustreadthefourchoicesmarkedA,B,CandD,anddecidewhichisthebestanswer.1.Whatdoesthemansuggestthewomando?A.Takeataxitotheairport.B.Bookaflightonline.C.Askherfriendforaride.D.Taketheshuttlebus.M:Areyouheadingtotheairporttomorrow?Iheardthetaxifarehasgoneupagain.W:Yes,butmyflightisat6a.m.Idon'tthinktheshuttlebusrunsthatearly.M:Whydon'tyouaskSarah?Shelivesnearbyandshe'sanearlybird.W:That'sagoodidea.I'llgiveheracalltonight.Q:Whatdoesthemansuggestthewomando?2.Whatdoesthewomanmean?A.Shehasalreadyfinishedthereport.B.Sheneedsmoretimetocompletethereport.C.Shedoesn'tknowhowtowritethereport.D.Shewantssomeoneelsetowritethereport.M:Howisyourannualreportcomingalong?ThedeadlineisthisFriday,youknow.W:I'vegatheredallthedata,butIstillneedtoanalyzetheresultsandwritetheconclusionsection.It'stakinglongerthanIexpected.M:IsthereanythingIcanhelpwith?W:Thanks,butIthinkIcanmanageifIworkthroughtheweekend.Q:Whatdoesthewomanmean?3.Wheredoesthisconversationmostlikelytakeplace?A.Atabookstore.B.Atalibrary.C.Atacoffeeshop.D.Atapostoffice.W:Excuseme,couldyoutellmewhereIcanfindbooksonenvironmentalscience?M:They'reonthesecondfloor,sectionB.Youcanalsosearchouronlinecatalogforspecifictitles.W:Great.AndhowlongcanIkeepthem?M:Threeweeksforundergraduates,andyoucanrenewthemonceonline.Q:Wheredoesthisconversationmostlikelytakeplace?4.Whatistheman'sopinionaboutthenewpolicy?A.Hethinksitistoostrict.B.Hebelievesitwillbeeffective.C.Heconsidersitunnecessary.D.Hethinksitneedsrevision.W:Haveyouheardaboutthenewcompanypolicy?Employeesarerequiredtoclockinby8:30everymorning.M:Well,Ithinkit'sabouttime.Somepeoplehavebeenarrivingat10andstillleavingat5.It'snotfairtothosewhoarriveearly.W:Butdon'tyouthinkit'sabittoorigid?M:Notreally.Disciplineisthefoundationofefficiency.Q:Whatistheman'sopinionaboutthenewpolicy?5.Whatarethespeakersmainlydiscussing?A.Atravelplanfortheholiday.B.Aresearchprojectonclimatechange.C.Apresentationschedule.D.Ajobinterviewpreparation.M:ProfessorLee,I'vebeenworkingontheoutlineformythesisonrenewableenergyinruralareas.Couldwediscussitnow?W:Ofcourse.Haveyouconsideredfocusingonsolarenergyadoptioninmountainvillages?There'ssomeinterestingdatafromtheTai'anregion.M:That'sexactlywhatIhadinmind.IvisitedavillagenearMountTailastmonthandcollectedsomefirsthandinformation.W:Excellent.Let'slookatthestructureofyourfirstchapter.Q:Whatarethespeakersmainlydiscussing?PartBDirections:Youwillhearseverallongerconversationsortalks.Aftereachconversationortalk,youwillbeaskedsomequestions.Theconversationsandquestionswillbespokenonlyonce.Afteryouhearaquestion,readthefourchoicesanddecidewhichisthebestanswer.Questions6and7arebasedonthefollowingconversation.W:Goodafternoon,GreenfieldMedicalCenter.HowmayIhelpyou?M:Hello,I'dliketomakeanappointmentwithDr.Wangforageneralcheck-up.I'manewpatient.W:Certainly.Dr.WangisavailableonTuesdaymorningorThursdayafternoonnextweek.Whichwouldyouprefer?M:Tuesdaymorningwouldbegreat.Whattimeistheearliestslot?W:Shehas8:00and9:15.I'drecommend8:00sinceit'syourfirstvisit—therewillbesomepaperworktofillout.M:8:00itis.MynameisLiWei.ShouldIbringanythingspecific?W:JustyourIDcardandanypreviousmedicalrecords,ifyouhavethem.Pleasearrive15minutesearlytocompletetheregistration.M:Noproblem.Thankyouverymuch.W:You'rewelcome.We'llseeyouonTuesdayat8.6.Whydoesthewomanrecommendthe8:00slot?A.Itistheonlyavailabletime.B.Thepatientneedstocompletepaperwork.C.Dr.Wangprefersearlymorning.D.Thepatienthasanotherappointmentat9:15.7.Whatdoesthepatientneedtobring?A.Areferralletterandinsurancecard.B.OnlyhisIDcard.C.HisIDcardandpreviousmedicalrecords.D.Acompletedregistrationform.Questions8to10arebasedonthefollowingtalk.Goodmorning,everyone.Welcometotoday'sseminaronsustainableurbandevelopment.I'mDr.ZhangfromtheSchoolofUrbanPlanningatShandongUniversity.TodayI'dliketosharesomefindingsfromourthree-yearresearchprojectongreentransportationinmedium-sizedChinesecities.Asmanyofyouknow,rapidurbanizationhasbroughtenormouschallengestocityinfrastructure.Trafficcongestion,airpollution,andnoisehavebecomedailystrugglesforurbanresidents.Ourresearchfocusedonthreecities—Tai'an,Zaozhuang,andLinyi—andexaminedhowpublicbicycle-sharingsystemsandelectricbusnetworkshavetransformedurbanmobility.Letmestartwithsomenumbers.InTai'analone,thepublicbike-sharingprogram,launchedin2018,nowhasover320stationsandmorethan8,000bicycles.Oursurveyof2,500residentsshowedthat43%ofrespondentsusethesystematleastthreetimesperweek.Moreimpressively,28%ofusersreportedthattheyhadreducedtheiruseofprivatevehiclessincetheprogrambegan.However,challengesremain.Maintenancecostshaverisensteadily,andduringpeakhours,manystationsrunoutofbikes.Wealsofoundthattheadoptionrateinsuburbanareasissignificantlylowerthaninthecitycenter,mainlyduetoinadequatestationcoverage.Theelectricbusnetwork,ontheotherhand,hasshownremarkableprogress.Allthreecitieshavereplacedatleast60%oftheirdieselbuseswithelectricones.InTai'an,thefigurestandsat72%,whichhascontributedtoameasurabledecreaseinPM2.5levelsalongmajorroutes.Lookingahead,werecommendthatcityplannersinvestinsmartdockingsystems,expandstationcoveragetosuburbanzones,andintegratebike-sharingwithbusroutestocreateaseamlessmultimodaltransportnetwork.Ourdatasuggeststhatsuchintegrationcouldincreaseoverallpublictransportationusageby15to20%.I'llnowmoveontodiscussthespecificpolicyrecommendationsinmoredetail...8.Whatisthemaintopicofthetalk?A.ThehistoryofurbandevelopmentinChina.B.Greentransportationinmedium-sizedChinesecities.C.Howtoreducetrafficaccidentsinurbanareas.D.TheexpansionofsubwaysystemsinShandong.9.Accordingtothesurvey,whatpercentageofrespondentsusethebike-sharingsystematleastthreetimesperweek?A.28%B.43%C.60%D.72%10.Whatdoesthespeakerrecommendforthefuture?A.Buildingmoresubwaylines.B.Investinginsmartdockingsystemsandexpandingcoverage.C.Replacingallbicycleswithelectricscooters.D.Increasingthepriceofpublictransportation.Questions11to13arebasedonthefollowingconversation.M:Hi,Linda.Iheardyou'vebeenselectedfortheexchangeprogram.Congratulations!W:Thanks,Tom.Yes,I'llbespendingonesemesterattheUniversityofEdinburgh.I'mexcitedbutalsoabitnervous.M:That'scompletelynormal.Whenareyouleaving?W:September15th.Thesemesterstartsonthe20th,soI'llhaveafewdaystosettlein.M:Haveyousortedoutyouraccommodationyet?W:That'swhatI'mworriedabout.Theuniversityofferedmeaplaceinastudentdorm,butI'vebeenthinkingaboutrentingaflatoff-campus.Itwouldgivememoreindependence.M:Isee.Butkeepinmindthatlivingoff-campuscanbemoreexpensiveandyou'llhavetohandlebillsandtransportation.WhenIwasonexchangeinManchesterlastyear,Istayedinadormanditwasactuallygreat.Imetsomanypeoplefromdifferentcountries.W:Thatdoessoundappealing.MaybeIshouldgowiththedormforthefirstsemesterandthendecideaboutmovingoff-campuslater.M:That'sasmartapproach.Also,haveyoulookedintothecoursesyouwanttotake?W:I'vebrowsedthecatalog.TheyhavesomefascinatingmodulesonScottishliteratureandculturalstudies.Iplantotaketwocoursesrelatedtomymajorandoneelectiveforfun.M:Goodplan.Anddon'tforgettoapplyforthescholarshipbeforeyouleave.ThedeadlineisendofJuly,right?W:Yes,July31st.I'mworkingontheapplicationessaynow.Actually,that'spartlywhyIwantedtotalktoyou.Wouldyoubewillingtoproofreaditforme?M:Ofcourse!SenditoverandI'llhavealookthisweekend.11.WhenwillLindaleaveforEdinburgh?A.September20th.B.September15th.C.July31st.D.Theconversationdoesnotmentionit.12.WhatconcerndoesLindahave?A.Shehasn'tbeenacceptedintotheprogram.B.Shedoesn'tknowwhichcoursestotake.C.Shehasn'tdecidedonaccommodation.D.Shecan'taffordthetuition.13.WhatdoesTomoffertodo?A.HelpLindafindaflat.B.ProofreadLinda'sscholarshipessay.C.DriveLindatotheairport.D.HelpLindachoosecourses.Questions14and15arebasedonthefollowingtalk.Welcometothisweek'seditionofScienceFrontiers.Today,we'relookingatafascinatingdevelopmentinthefieldofartificialintelligence—specifically,howAIisbeingusedtopreserveendangeredlanguages.Thereareapproximately7,000languagesspokenintheworldtoday,butlinguistsestimatethatnearlyhalfofthemareatriskofdisappearingbytheendofthiscentury.Whenalanguagedies,welosemorethanjustwords—weloseanentireculturalworldview,uniqueecologicalknowledge,andcenturiesofhumanwisdom.ResearchersatseveraluniversitieshavenowdevelopedAImodelscapableoflearningthegrammaticalstructuresandvocabularyofendangeredlanguagesfromverylimiteddata.Unlikeconventionaltranslationtoolsthatrequiremassivedatasets,thesenewmodelsusewhat'scalled"few-shotlearning"—theycangeneralizefromasfewasafewhundredsentences.OnegroundbreakingprojectinvolvestheTarianalanguage,spokenbyfewerthan100peopleintheAmazonregion.ByrecordingconversationswithelderlyspeakersandtraininganAIsystemonthoserecordings,researchershavecreatedadigitalarchivethatnotonlystoresthelanguagebutcanalsogeneratenewsentences,helpingyoungercommunitymemberslearntheirancestraltongue.However,criticshaveraisedethicalconcerns.SomearguethatAIcannotcapturethefullculturalcontextofalanguage—thegestures,thesocialsettingsinwhichcertainwordsareused,andthespiritualsignificanceofparticularphrases.Othersworrythattechnologymightcreateafalsesenseofsecurity,leadingcommunitiestostoptheirowneffortstopassonthelanguagenaturally.Despitetheseconcerns,theconsensusamongresearchersisthatAIshouldbeseenasasupplementarytoolratherthanareplacementforcommunity-basedlanguagepreservationefforts.Themostsuccessfulprogramscombinetechnologywithintergenerationallearning,whereeldersandyoungpeopleinteractdirectly,supportedbydigitalresources.14.Whatisthemainideaofthetalk?A.HowAIisthreateningtraditionallanguages.B.HowAIisbeingusedtopreserveendangeredlanguages.C.Whyhalfoftheworld'slanguageswilldisappear.D.ThehistoryoftheTarianalanguage.15.Whatconcerndocriticsraise?A.AIistooexpensiveformostcommunities.B.AIcannotcapturethefullculturalcontextofalanguage.C.AIproducestoomanyerrorsintranslation.D.AIwillreplacehumantranslatorscompletely.PartCDirections:Youwillhearapassage.Whilelistening,fillintheblanksnumbered16to20withtheexactwordsyouhear.Thepassagewillbereadtwice.Theconceptof"lifelonglearning"hasgainedsignificantattentioninrecentyears,andforgoodreason.Inaworldwheretechnologicaladvancementsarereshapingindustriesatanunprecedentedpace,theskillsweacquireinschooloruniversityarenolonger16tolastalifetime.Researchshowsthatprofessionalswhoengageincontinuouslearningarenotonlymore17intheircareersbutalsoreporthigherlevelsoflifesatisfaction.Oneofthemosteffectiveapproachestolifelonglearningisthepracticeof"microlearning"—breakingdowncomplexsubjectsintosmall,18unitsthatcanbestudiedinjust10to15minutesaday.Studiesindicatethatthismethodimprovesretentionratesbyupto40%comparedtotraditionallong-formstudysessions.Moreover,theriseofonlineplatformshasdemocratizedaccesstoeducation.A19bytheMinistryofEducationrevealedthatover65millionChineseadultsparticipatedinsomeformofonlinelearningin2024,afigurethatrepresentsa30%increasefromthepreviousyear.Themostpopularsubjectsweredigitalskills,foreignlanguages,andprofessional20.Expertspredictthatasthejobmarketcontinuestoevolve,theabilitytolearnnewskillsquicklywillbecomethemostvaluablecompetenceapersoncanpossess.SectionIIUseofEnglishReadthefollowingtext.Choosethebestwordforeachnumberedblank.Thehumanbrainisarguablythemostcomplexstructureintheknownuniverse.Weighingapproximately1.4kilograms,itcontainsroughly86billionneuronsconnectedbytrillionsofsynapses,forminga21ofsuchintricacythateventhemostadvancedsupercomputerscannotfully22itscapabilities.Forcenturies,scientistshavesoughttounderstandhowthisremarkableorganproducesconsciousness,memory,andemotion.TheancientEgyptiansbelievedthebrainwasa23organanddiscardeditduringmummification,whiletheheartwaspreservedastheseatofthesoul.ItwasnotuntiltheRenaissancethatserious24ofbrainanatomybegan,andonlyinthe19thcenturydidscientists25thatdifferentregionsofthebrainservedifferentfunctions.Modernneurosciencehasmade26strides.Wenowknowthatthebrain'sstructureisnot27,asoncebelieved,butchangesthroughoutourlivesinresponsetoexperience—apropertyknownasneuroplasticity.Thisdiscoveryhas28implicationsforrehabilitationafterbraininjury,education,andeventhetreatmentofmentaldisorders.29,thebrainremainsdeeplymysterious.Westilldonotfullyunderstandhowsubjective30—thefeelingofwhatitisliketoseethecolorredortastechocolate—arisesfromthefiringofneurons.Thisgapinourunderstandingiswhatphilosopherscallthe"hardproblem"of31.Recentadvancesinbrain-computerinterfaceshaveaddedanew32toneuroscience.Researchershavesuccessfullyusedimplantedelectrodestoallowparalyzedpatientstocontrolroboticlimbswiththeir33.Whilethesetechnologiesarestillintheir34,theyraiseprofoundethicalquestionsaboutprivacy,identity,andthevery35ofwhatitmeanstobehuman.Somescientistsbelievethatwithinthenextfewdecades,wemaydeveloptechnologiescapableof36mappingthebrain'sentireneuralnetwork—afeatthatwouldtransformourunderstandingofbothbiologyand37.Othersaremore38,notingthatthebrain'scomplexitymaypresent39challengesthatnoamountofcomputingpowercanovercome.40,whatisclearisthatthebrainwillcontinuetocaptivateandchallengeresearchersforgenerationstocome.21.A.networkB.tissueC.systemD.muscle22.A.imitateB.replicateC.createD.replace23.A.vitalB.uselessC.mysteriousD.secondary24.A.studyB.thoughtC.recordD.guess25.A.realizedB.dreamedC.deniedD.forgotten26.A.extraordinaryB.ordinaryC.limitedD.reversed27.A.changeableB.flexibleC.fixedD.broken28.A.fewB.noC.profoundD.harmful29.A.ThereforeB.NeverthelessC.MoreoverD.Thus30.A.experienceB.thoughtC.memoryD.dream31.A.biologyB.physicsC.consciousnessD.medicine32.A.problemB.dimensionC.obstacleD.risk33.A.handsB.feetC.thoughtsD.eyes34.A.maturityB.infancyC.peakD.end35.A.natureB.sizeC.weightD.color36.A.partiallyB.fullyC.barelyD.never37.A.chemistryB.astronomyC.physicsD.philosophy38.A.optimisticB.cautiousC.indifferentD.enthusiastic39.A.simpleB.minorC.insurmountableD.manageable40.A.HoweverB.ThereforeC.SimilarlyD.FortunatelySectionIIIReadingComprehensionPartAReadthefollowingtexts.AnswerthequestionsbychoosingA,B,CorD.Text1Inthepastdecade,thesharingeconomyhastransformedthewaypeopleconsumegoodsandservices.CompanieslikeAirbnb,Uber,andDidihavedisruptedtraditionalindustriesbyleveragingtechnologytoconnectconsumersdirectlywithproviders.Whileproponentsarguethatthismodelpromotesefficiency,reduceswaste,andcreateseconomicopportunitiesforindividuals,criticspointtoadarkersideofthephenomenon.Onemajorconcernistheerosionoflaborprotections.Workersinthesharingeconomyaretypicallyclassifiedasindependentcontractorsratherthanemployees,whichmeanstheydonotreceivebenefitssuchashealthinsurance,paidleave,orretirementcontributions.Thisleavesthemvulnerableduringeconomicdownturnsorpersonalemergencies.AstudybytheInternationalLabourOrganizationfoundthatgigworkersworldwideearn,onaverage,28%lessthanequivalentemployeeswhentotalcompensationistakenintoaccount.Anotherissueistheimpactonlocalhousingmarkets.Incitieswithhighconcentrationsofshort-termrentals,long-termrentalpriceshaverisensignificantly.Barcelona,forexample,sawrentalcostsincreaseby50%between2015and2023,atrendmanyattributetotheproliferationofAirbnblistings.Localresidents,particularlythoseinlowerincomebrackets,havebeenpricedoutoftheirownneighborhoods.Environmentalconsequencesarealsocomingunderscrutiny.Whilesharingplatformsclaimtopromotesustainabilitybymaximizingresourceutilization,researchsuggestsamorenuancedpicture.Ride-hailingservices,forinstance,havebeenshowntoincreasetotalvehiclemilestraveled,asdriversoftencirclebetweenfares.A2022studypublishedinNatureClimateChangeestimatedthatride-hailingcontributesanadditional20%ingreenhousegasemissionsperpassenger-milecomparedtoprivatecarownership.Despitethesechallenges,thesharingeconomyisunlikelytodisappear.Whatisneeded,accordingtopolicyexperts,isaregulatoryframeworkthatbalancesinnovationwithsocialresponsibility.Somecitieshavealreadytakensteps:Amsterdamhasimplementedstrictcapsonshort-termrentals,Californiahaspassedlegislationrequiringgigeconomycompaniestoreclassifycertainworkersasemployees,andseveralEuropeancountriesareexploringdigitaltaxationonplatformrevenues.Thefutureofthesharingeconomywilldependlargelyonwhetherstakeholders—platforms,workers,consumers,andgovernments—canfindamiddlegroundbetweenuncheckedmarketforcesandthepublicinterest.Asthesectormatures,thequestionisnolongerwhethertoregulate,buthowtodosoeffectively.41.Accordingtothepassage,whatisoneadvantageofthesharingeconomy?A.Itguaranteesworkers'benefitsandprotections.B.Itpromotesefficiencyandreduceswaste.C.Itlowersrentalpricesinmajorcities.D.Itreducesgreenhousegasemissions.42.ThestudybytheInternationalLabourOrganizationsuggeststhatgigworkers:A.earnmorethanregularemployees.B.receivebetterhealthbenefits.C.earnlessthanequivalentemployeeswhentotalcompensationisconsidered.D.preferbeingclassifiedasindependentcontractors.43.WhathappenedinBarcelonabetween2015and2023?A.Rentalcostsdecreasedby50%.B.ThenumberofAirbnblistingsdropped.C.Rentalcostsincreasedby50%.D.Long-termrentalpricesstabilized.44.Accordingtothe2022studyinNatureClimateChange,ride-hailingservices:A.reducevehiclemilestraveled.B.decreasegreenhousegasemissions.C.increasegreenhousegasemissionsperpassenger-milecomparedtoprivatecars.D.havenomeasurableenvironmentalimpact.45.Whatistheauthor'soverallattitudetowardthesharingeconomy?A.Stronglysupportive.B.Completelynegative.C.Balancedandadvocatingforeffectiveregulation.D.Indifferent.Text2TheancientSilkRoadwasnotmerelyatraderoute;itwasavastnetworkofculturalexchangethatshapedcivilizationsacrossEurasiafornearlytwomillennia.StretchingfromChang'an(modern-dayXi'an)totheMediterranean,thisnetworkcarriednotonlysilk,spices,andpreciousmetals,butalsoideas,religions,technologies,andevendiseases.MountTai,locatedinShandongProvince,playedauniqueroleinthisculturaltapestry.WhilenotdirectlyonthemainSilkRoadroute,itservedasaspiritualandculturalbeaconthatattractedpilgrims,scholars,andemperorsfromacrosstheempire.TheinscriptionsandtemplesonMountTai—somedatingbackover2,000years—recordthevisitsofcountlesshistoricalfiguresanddocumenttheevolutionofChinesereligiousandphilosophicalthought.TheconnectionbetweenMountTaiandtheSilkRoadismoresubtlethanonemightexpect.DuringtheTangDynasty(618–907CE),whenSilkRoadtradewasatitspeak,monkstravelingalongtheroutebroughtBuddhismfromIndiatoChina.ThisnewreligionmingledwithexistingConfucianandDaoisttraditions,manyofwhichwerecenteredonsacredmountainslikeTai.TheresultwasauniquelyChineseformofBuddhismthatincorporatedelementsofmountainworship,ancestorveneration,andimperialceremony.ArchaeologicalevidencefromtheShandongregionrevealstracesofforeigninfluenceeveninthiseasternprovince.GlassbeadsoriginatingfromtheMiddleEasthavebeenfoundintombsnearTai'an,andcertaindecorativemotifsonlocalpotteryshowCentralAsianartisticstyles.ThesefindingssuggestthattheeconomicandculturalripplesoftheSilkRoadextendedfarbeyonditsimmediategeographicpath.In1987,MountTaiwasdesignatedaUNESCOWorldNaturalandCulturalHeritagesite.Today,scholarscontinuetostudyitsinscriptions,architecture,andartifactstobetterunderstandhowChina'sculturalidentitywasshapedbybothinternaltraditionsandexternalinfluences.Themountainstandsasareminderthatcivilizationisrarelybuiltinisolation;itistheproductofcontinuousexchange,adaptation,andsynthesis.46.WhatwastheSilkRoadprimarily?A.Amilitaryroute.B.Anetworkofculturalandtradeexchange.C.AsingleroadfromXi'antoRome.D.Areligiouspilgrimageroute.47.WhatroledidMountTaiplayinrelationtotheSilkRoad?A.Itwasdirectlyonthemaintraderoute.B.IthadnoconnectiontoSilkRoadculture.C.ItservedasaspiritualandculturalbeaconinfluencedbySilkRoadexchanges.D.Itwasamajortradingpostforsilk.48.DuringwhichdynastywasSilkRoadtradeatitspeak?A.HanDynasty.B.TangDynasty.C.SongDynasty.D.MingDynasty.49.WhatarchaeologicalevidencenearTai'ansuggestsSilkRoadinfluence?A.Buddhisttemples.B.GlassbeadsfromtheMiddleEast.C.Silkfragments.D.Romancoins.50.Whatisthemainideaofthepassage?A.MountTaiisthemostimportantsiteontheSilkRoad.B.TheSilkRoadhadnoimpactonShandongProvince.C.MountTaiandtheSilkRoadwereconnectedthroughculturalexchangeandinfluence.D.MountTaiwasdesignatedaUNESCOsitein1987.Text3Depressionisoneofthemostprevalentmentalhealthconditionsworldwide,affectinganestimated280millionpeopleaccordingtotheWorldHealthOrganization.Despiteitsprevalence,treatmentremainsfarfromstraightforward.Antidepressantmedications,primarilyselectiveserotoninreuptakeinhibitors(SSRIs),areeffectiveformanypatientsbutcomewithsignificantlimitations:theyoftentakefourtosixweekstoshowresults,producesideeffectsinupto50%ofusers,andfailtoprovideadequatereliefforroughlyone-thirdofpatients—aconditionclinicianscall"treatment-resistantdepression."Inrecentyears,however,asurprisingcandidatehasemergedfromanunexpectedcornerofmedicine:ketamine.Originallydevelopedasananestheticinthe1960sandlaterknownasarecreationaldrug,ketaminehasshownremarkableantidepressanteffectswhenadministeredincontrolledclinicalsettings.Unlikeconventionalantidepressants,ketaminecanproduceimprovementswithinhoursofadministration,makingitparticularlyvaluableforpatientsinacutedistress.ThemechanismbywhichketamineworksdiffersfundamentallyfromthatofSSRIs.WhileSSRIstargettheserotoninsystem,ketamineactsontheglutamatesystem—thebrain'sprimaryexcitatoryneurotransmitter.Researchsuggeststhatketaminestimulatestheproductionofbrain-derivedneurotrophicfactor(BDNF),aproteinthatpromotesthegrowthofnewneuralconnections.Thispropertyhasledscientiststoreconsiderthebiologicalbasisofdepressionitself:ratherthansimplya"chemicalimbalance,"depressionmayinvolveactualstructuralchangesinthebrainthatketaminehelpstoreverse.However,ketaminetreatmentisnotwithoutcontroversy.Thedrug'spotentialforabuseanditsdissociativeeffects—includinghallucinationsandfeelingsofdetachmentfromreality—haveraisedconcerns.Long-termeffectsremainpoorlyunderstood,asmoststudieshavetrackedpatientsforonlyafewweeksormonths.Additionally,thecostoftreatmentcanbesubstantial;asingleinfusionsessioncancostbetween400aIn2019,theU.S.FoodandDrugAdministrationapprovedesketamine,anasalsprayderivedfromketamine,fortreatment-resistantdepression.Theapprovalcamewithstrictguidelines:thedrugmustbeadministeredinacertifiedmedicalfacility,andpatientsmustbemonitoredforatleasttwohoursaftereachdose.Theserequirementsreflectthedelicatebalancebetweenmakinginnovativetreatmentsavailableandensuringpatientsafety.Criticsalsopointtoadeeperissue:themedicalizationofmentalhealth.Theyarguethatdepressionisnotpurelyabiologicaldisorderbutisdeeplyintertwinedwithsocial,economic,andpsychologicalfactors—isolation,poverty,trauma,andmeaninglessness.Nodrug,howevereffective,canaddresstheserootcauses.Asonepsychiatristnoted,"Apillcannotgivesomeoneapurposeinlife."51.Accordingtothepassage,whatpercentageofpatientshave"treatment-resistantdepression"?A.Upto50%B.Roughlyone-thirdC.280millionD.Thepassagedoesnotspecify.52.HowdoesketaminedifferfromSSRIsintermsofspeedofeffect?A.Ketaminetakeslongertowork.B.Ketamineproducesimprovementswithinh