2026年托福《听力》iBT真题

2026年托福《听力》iBT真题

Conversation1

Narrator:Listentoaconversationbetweenastudentandaprofessor.

Professor:Goodafternoon,Sarah.Yousentmeanemailearlierabouttheindependentstudyproposalfornextsemester.DidyouhaveachancetolookovertheguidelinesIsent?

Student:Hi,Dr.Aris.Yes,Idid.That’sactuallywhyIwantedtomeet.I’mreallyinterestedinthetopicofurbanagriculture,specificallyverticalfarminginhigh-densityenvironments.ButI’mabitworriedaboutthescope.Theguidelinessuggestfocusingonalocalcasestudy,butI’mfindingithardtogetdatafromthelocalfarmshereinthecity.

Professor:Thatisacommonhurdle.Manyofthecommercialoperationsherearehesitanttoshareproprietarydataabouttheircropyieldsorenergyusage.However,thegoaloftheindependentstudyisn'tnecessarilytogetaccesstotradesecrets.It’stoapplythetheoreticalframeworkswe’vediscussedinclasstoareal-worldscenario.

Student:So,maybeIdon'tneedtheirexactelectricalbills?Icouldfocusonthearchitecturaldesignandthetheoreticalresourceefficiencyinstead?

Professor:Exactly.Youcouldmodelthepotentialoutputbasedonsquarefootageandpublishedscientificliteratureonhydroponicsystems.Haveyoulookedintothe"GreenSky"projectdowntown?It’saprivate-publicpartnership.

Student:Isawthatbuilding!Ithastheglassfacadewiththeintegratedhydroponicpanels.ButIassumedIcouldn'tstudyitbecauseit’saprivatecompanyrunningit.

Professor:Theyactuallypublishanannualsustainabilityreportforthecitycouncilaspartoftheirzoningagreement.Itmightnothavethegranulardatayouwant,butithasaggregatedataonwaterusageandwastereduction.Thatcouldbeasolidfoundationforyouranalysis.

Student:Thatsoundsperfect.Iwasalsothinkingaboutcomparingtheirverticalsetupwithatraditionalrooftopgarden.Wouldthatbetoomuchforasinglesemester?

Professor:Acomparativeanalysisisambitious,butifyoustructureitwell,itshowsdepth.Justbecarefulnottooverextendyourself.Perhapsfocusononemetric—likewaterconsumptionefficiencyperkilogramofproduce—ratherthantryingtocompareeverything.

Student:Waterefficiencywouldbeinterestingbecauseverticalfarmingoftenusesrecirculatingsystems,whereasrooftopgardensmightlosemoretoevaporation.

Professor:Precisely.That’satestablehypothesis.Whydon'tyoudraftatwooutlinewiththespecificdatapointsyouneedfromthatsustainabilityreport?Ifyoucanidentifywhat’spubliclyavailable,wecandiscussifyouneedtosupplementitwithgeneralliterature.

Student:Okay,I’lldothat.IshouldhaveittoyoubyFriday.

Professor:Thatworks.AndSarah,don’tforgettocitethezoningregulations.Theyoftendictatethelimitationsonwaterrunoff,whichdirectlyimpactsthefarmingmethodsused.

Student:Oh,goodpoint.Ihadn'tconsideredthelegalaspect.Thanks,Dr.Aris.

Professor:Noproblem.SeeyouFriday.

1.Whydoesthestudentgotoseetheprofessor?

A.Toaskforanextensiononacurrentassignment.

B.Todiscussdataaccessforherindependentstudyproposal.

C.Tocomplainaboutthelackoflocalverticalfarms.

D.Togetapprovalforazoningregulationchange.

2.Whatistheprofessor'sopinionofthestudent’sinitialconcernaboutdata?

A.Heagreesthattheprojectisimpossiblewithoutproprietarydata.

B.Hesuggestsshechangehertopicentirelytoarchitecture.

C.Hebelievestheoreticalframeworksandpublicdataaresufficient.

D.Heofferstogiveherhisownprivateresearchdata.

3.Whatdoestheprofessorsuggestthestudentuseasaprimarydatasource?

A.Interviewswiththe"GreenSky"projectengineers.

B.Theannualsustainabilityreportpublishedforthecitycouncil.

C.Theproprietaryelectricalbillsoflocalfarms.

D.Asurveyoftraditionalrooftopgardeners.

4.Whatdoestheprofessoradviseregardingthecomparativeanalysis?

A.Toavoidcomparisonsastheyaretoocomplex.

B.Tofocusonasinglemetriclikewaterefficiency.

C.Tocompareonlythearchitecturalstyles.

D.Toincludeasmanymetricsaspossibleforaccuracy.

5.Whatadditionalfactordoestheprofessorremindthestudenttoconsider?

A.Thecostofhydroponicequipment.

B.Thezoningregulationsregardingwaterrunoff.

C.Thetastedifferencebetweenverticallyandtraditionallygrowncrops.

D.Thelaborrequirementsforharvesting.

Lecture1

Narrator:ListentopartofalectureinaGeologyclassGeology.

Professor:Okay,let'scontinueourdiscussiononplatetectonics.We’vecoveredthebasics:divergentboundarieswhereplatesmoveapart,andconvergentboundarieswheretheycollide.Today,Iwanttofocusonaspecificphenomenonthatoccursatconvergentboundaries,particularlywhereanoceanicplatesubductsbeneathacontinentalplate.We'retalkingaboutvolcanicarcs,butmorespecifically,themechanicsofmagmageneration.

Now,manypeoplethinkmagmaisjustliquidrockwaitingtoerupt.Butgeologically,thegenerationofmagmainsubductionzonesisquitecomplex.Itdoesn'tjustmeltbecausetheplateisgettingdeeperandhotter.Infact,astheoceanicplatesubducts,thepressureincreases,whichactuallyraisesthemeltingpointoftherock.So,ifanything,therockshouldstaysolid.

So,howdoesitmelt?Thekeyiswater.Theoceaniccrustissaturatedwithwater,bothfromtheoceanaboveandhydratedmineralswithinthecrustitself.Asthisplateisforceddownintothemantle,theincreasingpressureandtemperaturecausethemineralstobecomeunstable.Theyreleasetheirwater—thisprocessiscalleddehydration.Thiswaterrisesintotheoverlyinghotmantlewedge.

Now,hereisthecrucialphysicalchemistryconcept:wateractsasaflux.Itlowersthemeltingtemperatureofthemantlerock.Eventhoughthetemperatureofthemantlemightnotchangesignificantly,theadditionofwaterreducesthetemperaturerequiredtoturnsolidrockintoliquidmagma.Thisprocessisknownas"fluxmelting."

Oncethismagmaforms,beinglessdensethanthesurroundingsolidrock,itstartstorise.Butitdoesn'tjustrisestraightup.Itoftenpoolsinmagmachambers.Andthisiswherethingsgetinteresting.Themagmaisn'tuniform.Asitsitsinthechamber,itcoolsandcrystallizes.Themineralsthatcrystallizefirst—usuallyolivineandpyroxene—aredenserthanthemagmaandsettletothebottom.Thisleavestheremainingmagmaenrichedinsilicaandgases.Wecallthisprocessfractionalcrystallization.

Thischangeincompositionisvitalbecauseitdeterminestheexplosivenessoftheeventualeruption.Magmawithhighsilicacontentisviscous;it'sthickandsticky.Ittrapsgasbubbles.Whenthepressurefinallybuildsupenoughtobreaktherockabove,thegasexpandsviolently,resultinginanexplosiveeruption.Ontheotherhand,magmawithlowersilicaflowsmoreeasily,allowinggasestoescapegently,leadingtoeffusiveeruptions,likethoseinHawaii.

So,whenwelookatavolcanicarc,liketheCascadeRangeinthePacificNorthwest,weareseeingtheresultofthismulti-stageprocess:subduction,dehydration,fluxmelting,ascent,andfractionalcrystallization.It’safascinatinginterplayofchemistryandphysics.

6.Whatisthemaintopicofthelecture?

A.Thedifferencesbetweendivergentandconvergentboundaries.

B.Theprocessofmagmagenerationinsubductionzones.

C.Thecomparisonofexplosiveandeffusiveeruptions.

D.Themineralcompositionoftheoceaniccrust.

7.Accordingtotheprofessor,whydoesthesubductingplatenotmeltduetotemperature?

A.Thetemperaturedecreasesasdepthincreases.

B.Thepressureincreases,whichraisesthemeltingpoint.

C.Theplateisprotectedbyalayerofsediment.

D.Themantlewedgeistoocoldtomelttherock.

8.Howdoeswatercontributetomagmaformation?

A.Itincreasesthepressureontherock.

B.Itraisesthemeltingtemperatureofthemantlerock.

C.Itactsasafluxthatlowersthemeltingtemperature.

D.Itcoolstherockdownrapidly.

9.Whathappensduringfractionalcrystallization?

A.Magmamixeswithsedimentfromtheoceanfloor.

B.Densemineralssettle,leavingtheremainingmagmaenrichedinsilica.

C.Waterisaddedtothemagmachambertomakeitexplode.

D.Themantlewedgesolidifiescompletely.

10.Whydoeshigh-silicamagmaleadtoexplosiveeruptions?

A.Itishotterandexpandsfaster.

B.Itislessdenseandrisesquicker.

C.Itisviscousandtrapsgasbubblesuntilpressurebuildsup.

D.Itcontainsmorewaterfromthesubductingplate.

11.Whatexampledoestheprofessorgivetoillustratetheconcept?

A.TheHawaiianIslands.

B.TheMid-AtlanticRidge.

C.TheCascadeRange.

D.TheSanAndreasFault.

12.Howdoestheprofessororganizethelecture?

A.Bylistingdifferenttypesofvolcanoesaroundtheworld.

B.Bydescribingthestepsoftheprocessinchronologicalorder.

C.Bycomparingthetheoriesoftwofamousgeologists.

D.Bydefiningkeytermsinalphabeticalorder.

Conversation2

Narrator:Listentoaconversationbetweenastudentandauniversitystaffmember.

StaffMember:HousingOffice,Jacobspeaking.HowcanIhelpyou?

Student:Hi,Jacob.ThisisMike.I’mcallingaboutthedormitorymaintenancerequestIputinlastweek.Mysinkintheapartmentisdrainingreallyslowly,andnowthere’saweirdsmellcomingfromit.

StaffMember:Letmepullupyourrecord...Okay,foundit.Request492-Bforapartment304.ItsaysherethatatechnicianwasdispatchedonTuesday.

Student:Yeah,aguycameandlookedatit.Hepouredsomechemicaldraincleanerdownit,butitdidn’treallyhelp.Thewaterisstillbackingup,andthesmellisactuallygettingworse.Itsmellslikesewage.

StaffMember:I’msorrytohearthat.Usually,thechemicalcleanerclearsoutminorclogscausedbygreaseorhair.Ifitdidn'twork,theblockagemightbefurtherdowntheline,pasttheP-trap.

Student:TheP-trap?

StaffMember:Yes,it'sthecurvedpipeunderthesinkdesignedtoholdwaterandpreventsewergasesfromcomingup.Iftheblockageisinthemainstackorthebranchline,wemightneedtosnakeit.Sincethefirstattemptfailed,Ineedtoescalatethistotheplumbingteam.

Student:Okay,butthesmellismakingithardtobeinthekitchen.IsthereanythingIcandointhemeantime?

StaffMember:Youcantryrunningthefanandkeepingthedoorclosed.Also,makesureyouaren'tpouringanyoilorfoodscrapsdownthereuntilwefixit.Icanmarkthisas"Urgent-HealthHazard."Thatshouldgetsomeoneouttherewithin24hours.

Student:Thatwouldbegreat.Ihaveastudygroupcomingovertomorrownight,andIreallydon'twantthemtosmellthat.

StaffMember:Understood.I’llupdatetheticketnow.Youshouldreceiveaconfirmationemailwiththenewtimeslot.Isthereanythingelse?

Student:No,that’sall.Thanksforyourhelp,Jacob.

StaffMember:Noproblem,Mike.Sorryfortheinconvenience.

13.WhyisthestudentcallingtheHousingOffice?

A.Tocomplainaboutanoisyneighbor.

B.Toreportafailedmaintenanceattempt.

C.Torequestaroomtransfer.

D.Toaskaboutthehousingcontract.

14.Whatwastheresultofthefirstmaintenancevisit?

A.Thetechnicianreplacedthesink.

B.Thetechnicianusedchemicaldraincleaner,buttheproblempersisted.

C.Thetechniciancouldnotfindtheapartment.

D.Thestudentrefusedtoletthetechnicianin.

15.Whatdoesthestaffmemberimplyisthelikelycauseofthesmell?

A.AblockagelocatedpasttheP-trap.

B.Foodscrapsleftonthecounter.

C.Abrokenwindowseal.

D.Thechemicalcleanerusedbythetechnician.

16.Whatdoesthestaffmemberoffertodo?

A.Refundthestudent’shousingfees.

B.Sendacleaningcrewimmediately.

C.Escalatetherequesttotheplumbingteamasanurgenthealthhazard.

D.Teachthestudenthowtofixthesinkhimself.

17.Whatdoesthestudentimplyabouthissituation?

A.Heisplanningtomoveoutsoon.

B.Heisconcernedaboutguestscomingover.

C.Heisaplumberandknowshowtofixit.

D.Hecausedthecloghimself.

Lecture2

Narrator:ListentopartofalectureinanArtHistoryclass.

Professor:Todaywearedivingintotheearly20thcentury,aperiodofradicalexperimentation.We’vetalkedaboutCubismanditsfragmentationofform.Now,weturntoSurrealism.Emerginginthe1920s,largelyundertheinfluenceofthewriterAndréBreton,Surrealismwasdeeplyinterestedintheunconsciousmind.Breton,atrainedphysician,washeavilyinfluencedbythepsychoanalytictheoriesofSigmundFreud.

Freudbelievedthatourrepresseddesiresandfearssurfaceinourdreams.TheSurrealistswantedtotapintothis"sur-reality,"therealityabovethereal,tounlockthetruecreativepowerofthemind.Theydidn'twanttojustpaintabowloffruit;theywantedtopaintthefeelingoffearordesirethatabowloffruitmightrepresentinadream.

Oneofthetechniquestheyusediscalled"frottage."Letmewritethatontheboard.Frottage.ItwasdevelopedbytheartistMaxErnst.Imaginetakingapieceofpaperandplacingitoveraroughsurface,likeawoodenfloorboardoragrating.Then,yourubapencilorcharcoaloverthepaper.Thetextureoftheobjectbeneathistransferredtothepaper.Ernstwouldthenlookattheserandomtexturesandinterpretthem.Hemightseeabirdoraforestinthegrainofthewood.Thisprocessmimicsthewaythemindprojectsimagesontorandomvisualstimuli,likeseeingshapesinclouds.

AnotherkeyartistisSalvadorDalí.Dalíisfamousforhis"hand-painteddreamphotographs."Heusedamethodhecalledthe"paranoiac-criticalmethod."Thissoundsintense,butessentially,itwasawaytoinduceahallucinatorystatevoluntarily.Hewouldstareatanobjectuntilhisperceptionofitshifted,untilhesawsomethingelseentirely.Then,hewouldpaintthatdoubleimage.

Considerhisfamouspainting,"ThePersistenceofMemory."Youknowtheonewiththemeltingclocksdrapedoveralandscape.Thesoft,meltingformsdefythelawsofphysics.Theyrepresentthefluidityoftimeinthedreamstate,wheretimedoesn'texistinalinear,rigidway.Bydistortingthesehard,metallicobjectsintosoft,organicshapes,Dalíwaschallengingtheviewer'srelianceonthe"real"worldandinvitingthemintothesubconscious.

However,Surrealismwasn'tjustaboutpainting.Itwasamovementthatincludedsculpture,photography,andevenfilm.ButwhetheritwasapaintingbyRenéMagritte,whoplacedwordsandimagesincontradictoryways,orasculpturebyAlbertoGiacometti,thegoalremainedthesame:toresolvethecontradictoryconditionsofdreamandrealityintoanabsolutereality,asuper-reality.

18.Whatisthemainpurposeofthelecture?

A.TocomparethetechniquesofCubismandSurrealism.

B.ToexplaintheinfluenceofSigmundFreudonmodernmedicine.

C.ToexplorethegoalsandtechniquesoftheSurrealistmovement.

D.TocritiquethepoliticalmotivationsofAndréBreton.

19.Accordingtotheprofessor,whatwastheSurrealistviewofthe"real"world?

A.Itwastheonlysourceofartistictruth.

B.Itwaslessimportantthantheunconsciousmind.

C.Itwastoobeautifultobechanged.

D.Itwasimpossibletorepresentvisually.

20.Howdoestheprofessordefinethetechniqueof"frottage"?

A.Paintingdirectlyontoawoodensurface.

B.Rubbingapenciloverpaperplacedonatexturedsurface.

C.Staringatanobjectuntilitappearstochangeshape.

D.Creatingasculpturefrommeltedmetal.

21.WhydoestheprofessormentionMaxErnst?

A.Tocriticizehislackofformaltraining.

B.Toexplaintheparanoiac-criticalmethod.

C.Toillustratethetechniqueoffrottage.

D.TodiscusshispoliticaldisagreementswithBreton.

22.WhatdoestheprofessorimplyaboutSalvadorDalí's"ThePersistenceofMemory"?

A.ItisarealisticdepictionofaSpanishlandscape.

B.Itwascreatedusingthetechniqueoffrottage.

C.Themeltingclockssymbolizethefluidityoftimeindreams.

D.Itwasoriginallyasculpturebeforeitwasapainting.

23.WhatpointdoestheprofessormakeaboutRenéMagritte?

A.Hefocusedprimarilyonsculpture.

B.Heusedcontradictionsbetweenwordsandimages.

C.HewasthefounderoftheSurrealistmovement.

D.HerejectedFreud'stheories.

24.Organizethefollowingintheorderinwhichtheyarepresentedinthelecture.

A.TheinfluenceofFreud->Thetechniqueoffrottage->Dalí’smeltingclocks->Sculptureandfilm.

B.Dalí’smeltingclocks->Thetechniqueoffrottage->TheinfluenceofFreud->Sculptureandfilm.

C.Sculptureandfilm->TheinfluenceofFreud->Thetechniqueoffrottage->Dalí’smeltingclocks.

D.TheinfluenceofFreud->Sculptureandfilm->Dalí’smeltingclocks->Thetechniqueoffrottage.

Lecture3

Narrator:ListentopartofalectureinaPhysicsclass.

Professor:We’vespentthelastfewweeksdiscussingclassicalmechanicsandthelawsofmotionasdefinedbyNewton.Today,wearegoingtotouchonsomethingthatchallengesourintuition:QuantumEntanglement.Now,thisisacomplextopic,butIwantyoutograspthefundamentalparadoxbecauseitrepresentsoneofthestrangestaspectsofmodernphysics.

Inclassicalphysics,ifyouhavetwoobjects,let'ssaytwobilliardballs,andyouseparatethem,whathappenstoonehasabsolutelynoeffectontheother.Theyareindependententities.IfyoumeasurethepositionofballA,youknownothingaboutballBunlessyoumeasureitorlookatit.

Inquantummechanics,thingsaredifferent.Entanglementisaphenomenonwheretwoparticlesbecomelinkedinsuchawaythattheyshareasinglequantumstate.Imagineyouhaveapairofelectronsgeneratedfromthesameevent.Theyflyoffinoppositedirections.Accordingtotheprincipleofconservationofangularmomentum,ifoneelectronhas"spinup,"theothermusthave"spindown."

Hereistheweirdpart.Untilyoumeasureoneoftheparticles,itdoesn'tactuallyhaveadefinitespin.Itexistsinasuperpositionofstates—itisbothspinupandspindownsimultaneously.It’sonlytheactofmeasurementthatforcesitto"choose"astate.

Einsteinfamouslycalledthis"spookyactionatadistance."HefoundithardtoacceptthatmeasuringparticleAhereonEarthwouldinstantlycauseparticleB,perhapslightyearsaway,toassumetheoppositestate.Itseemstoviolatethecosmicspeedlimit,thespeedoflight.Howcaninformationtravelfasterthanlight?

Fordecades,physicistsdebatedwhetherthiswasarealphysicaleffectorjustaflawinourunderstanding—maybetherewere"hiddenvariables"wecouldn'tseethatpredeterminedthespins.However,inthe1960s,aphysicistnamedJohnBellproposedatheorem—Bell'sTheorem—whichprovidedawaytotestthis.Andlaterexperiments,notablybyAlainAspectinthe1980s,showedthatthesehiddenvariablesdon'texist.Theentanglementisreal.

So,whatdoesthismeanforus?Whilewecan'tuseittosendMorsecodemessagesfasterthanlight—becausetheresultofthemeasurementisrandom—itiscrucialfortheemergingfieldofquantumcomputing.Inaclassicalcomputer,abitiseithera0ora1.Inaquantumcomputer,qubitscanbeentangled.Thisallowsthecomputertoperformmassivecalculationsinparallel,solvingproblemsthatwouldtakeatraditionalcomputermillionsofyears.

Themathematicaldescriptionofthisinvolvesthewavefunction,oftendenotedbytheGreekletterPsi(Ψ).Whentwoparticlesareentangled,youcannotdescribethewavefunctionofonewithouttheother.Thetotalwavefunctionisaproductoftheindividualstates,butnotasimpleproduct—it'sasumofprobabilitiesthatlinkstheminseparably.

25.Whatisthemaintopicofthelecture?

A.Thelawsofmotioninclassicalmechanics.

B.Thedevelopmentofthequantumcomputer.

C.ThephenomenonofQuantumEntanglement.

D.ThelifeandworkofAlbertEinstein.

26.Howdoestheprofessorintroducethetopic?

A.Bycontrastingclassicalphysicswithquantummechanics.

B.BytellingastoryaboutJohnBell.

C.Bydefiningthespeedoflight.

D.Byexplaininghowtobuildaquantumcomputer.

27.Whatistheprofessor'spointaboutthebilliardballs?

A.Theyareanexampleofentangledparticles.

B.Theyrepresentindependentobjectsinclassicalphysics.

C.Theymovefasterthanthespeedoflight.

D.Theyhaveawavefunction.

28.Accordingtothelecture,whathappenswhenanentangledparticleismeasured?

A.Itchangesitsmass.

B.Itinstantlydeterminesthestateofitsentangledpartner.

C.Itsendsasignaltotheotherparticleatthespeedoflight.

D.Itdestroystheotherparticle.

29.WhydoestheprofessormentionEinstein?

A.Toexplainthemathematicalproofofentanglement.

B.Toshowthatheinitiallysupportedthetheoryofhiddenvariables.

C.Toillustratethecounter-intuitivenatureofthephenomenon.

D.Togivecreditfortheinventionofthequantumcomputer.

30.WhatwasthesignificanceofBell'sTheorem?

A.Itprovedthatinformationcantravelfasterthanlight.

B.Itshowedthathiddenvariablesdonotexplainentanglement.

C.ItdescribedthewavefunctionΨ.

D.ItallowedfortheinventionoftheMorsecode.

31.Whatpotentialapplicationofentanglementdoestheprofessormention?

A.Improvingclassicalbilliardballgames.

B.Sendinginstantmessagesacrossthegalaxy.

C.Increasingtheprocessingpowerofcomputers.

D.Generatingelectricityforspaceships.

32.Whatdoestheprofessorimplyaboutthewavefunction?

A.Itiseasytocalculateforsingleparticles.

B.ItisrepresentedbytheGreekletterAlpha.

C.Forentangledparticles,thestatesareinseparable.

D.Itisnotrelevanttomodernphysics.

Lecture4

Narrator:ListentopartofalectureinanEcologyclass.

Professor:Todaywe’regoingtolookataconceptcalled"TrophicCascades."Thistermdescribeshowchangesinthefoodwebcanhaverippleeffectsthatgofarbeyondtheimmediateinteraction.Specifically,weoftenseetop-downregulation,wherethepresenceorabsenceofatoppredatoraffectstheentireecosystem,includingthevegetation.

TheclassicexampleofthisisthereintroductionofgraywolvestoYellowstoneNationalParkin1995.Beforethewolvesreturned,theelkpopulationinYellowstonehadexplodedbecausetherewerenonaturalpredatorstokeeptheirnumbersincheck.Theelkspentalotoftimeintherivervalleysandnearthestreams,browsingontheyoungwillowandaspentrees.

Thisover-browsinghadadevastatingeffectonthevegetation.Thewillowsandaspenscouldn'tgrowtallenoughtoreproduceeffectively.Thisledtoadeclineinthebeaverpopulation,becausebeaversrelyonwillowandaspenforfoodandforbuildingtheirdamsandlodges.Withoutbeavers,thedamsfailed,whichchangedthehydrology—thewaterflow—ofthestreams.Thisaffectedthefishpopulationsandthebirdsthatlivedinthewetlands.

So,theecosystemwasdegraded,notjustbecauseoftheoverpopulationofelk,butbecauseoftheabsenceofthewolf.

Whenwolveswerereintroduced,theydidn'tjustkillelk.Theychangedtheelk'sbehavior.Thisisknownasthe"EcologyofFear."Theelkcouldnolongercasuallybrowseintheopenrivervalleysbecausethat'swheretheyweremostvulnerabletoambush.Theymovedtohigherground,intotheforestswheretheycouldseebetterandhide.

Asaresult,therivervalleyswererelievedfromtheconstantgrazingpressure.Thewillowsandaspensbegantoregenerate.Theygrewtallerandstronger.Withthereturnofthevegetation,thebeaverscameback.Theybuiltdams,whichcreatedponds.Thesepondstrappedsedimentandcooledthewater.

Thisisthetrophiccascade.Thetoppredator(thewolf)alteredthebehavioroftheherbivore(theelk),whichalteredthevegetation(thewillows),whichalteredtheecosystemengineers(thebeavers),whichalteredthephysicallandscape(therivers).

It'sapowerfulreminderthatnatureoperatesasacomplex,interconnectedsystem.Weusedtothinkthatifwemanagedthebottomofthefoodweb—likecontrollingthenumberofelkbyhuntingthemourselves—wecouldfixtheproblem.Butthisexampleshowsthatwecannotsimplyreplacetheroleofatoppredator.Humanhuntersdon'tcreatethesame"landscapeoffear"asawildpredatorthatispresent24/7.Theelkfearthewolfconstantly,whereastheyonlyfearhuntersduringhuntingseason.

33.Whatisthemainpurposeofthelecture?

A.TodiscussthehistoryofYellowstoneNationalPark.

B.ToexplaintheconceptofTrophicCascadesusingtheYellowstonewolves.

C.Toargueagainstthehuntingofelkinnationalparks.

D.Todescribethematinghabitsofgraywolves.

34.Accordingtotheprofessor,whathappenedtotheelkpopulationbeforethewolvesreturned?

A.Itwasnearlyextinctduetodisease.

B.Itwascontrolledbyhumanhunters.

C.Itincreasedandover-browsedvegetation.

D.Itmovedtothemountainstoescapetheheat.

35.Howdidtheabsenceofwolvesaffectthebeaverpopulation?

A.Beaverswereeatenbythewolves.

B.Beavershadnofoodbecausethewillowswereover-browsed.

C.Beaversmovedtoadifferentnationalpark.

D.Beaverswerehuntedbytheelk.

36.Whatdoestheprofessormeanbythe"EcologyofFear"?

A.Theelkwereafraidofthetouristsinthepark.

B.Thewolveswereafraidoftherangers.

C.Theelkchangedtheirbehaviortoavoidareaswherewolvesmighthunt.

D.Thebeaversstoppedbuildingdamsoutoffear.

37.Whatwastheresultofthewolves'returnonthephysicallandscape?

A.Theriversbecamewiderandfaster.

B.Thesoilerodedduetolackofvegetation.

C.Theriverschangedcourseduetobeaverdams.

D.Theforestsweredestroyedbythewolves.

38.Whydoestheprofessormentionhumanhunters?

A.Toshowthattheyaremoreeffectivethanwolves.

B.Toexplainwhyhuntingwasbannedin1995.

C.Tocontrasttheireffectonelkbehaviorwiththatofwolves.

D.Tosuggestthathuntersshouldmimicwolfbehavior.

39.Whatcanbeinferredaboutthelecturer'sviewofecosystems?

A.Theyaresimpleandeasytomanage.

B.Theyarefragileandeasilydestroyedbyhumans.

C.Theyarecomplexsystemswherepredatorsplayacrucialrole.

D.Theyshouldbemanagedbyremovingtoppredators.

Conversation3

Narrator:Listentoaconversationbetweenastudentandalibrarian.

Librarian:Referencedesk,canIhelpyou?

Student:Hi,yes.I’mworkingonapaperformyhistoryclass,andIneedtofindsomeprimarysourcesaboutthedailylifeoffactoryworkersintheearly1900shereinthecity.I’velookedattheonlinecatalog,butI’mnotsurewheretostart.

Libr