2021年 模擬試題 托業(yè)聽(tīng)力閱讀口語(yǔ)寫(xiě)作考試樣題 含答案及解析

20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題2021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)2021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題含答案及解析第一部分口語(yǔ)寫(xiě)作考試樣題含答案及解析T1Somecollegestudentstakeclassesduringthesummer.Otherstakethesummerofffromschool,sothattheycanrestorworkatajob.Whichdoyouthinkisbetterforstudents?Explainwhy.T2Reading：AllowStudentstoParkinFacultyParkingLotIwouldliketoproposethatstudentswholiveoffcampusanddrivetoschoolbeallowedtoparkintheemployeeparkinglotbehindMessnerHall,whichiscurrentlyreservedforuniversityfaculty.FindingaparkingspotnearClassroombuildingsisdifficult—weoftenhavetodrivearoundlookingforaplacetopark,whichmakesuslatetoclass.Thefacultylotisn’tfullyused—IseealotofemptyspacesthereinthemornigandsoIdon’tthinkitwouldbeinconvenientfortheuniversitytoalsoallowstudentswhodrivetoschooltoparkthere.SincerelyGregMurphy20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Question：Thewomanexpressesheropinionabouttheproposaldescribedintheletter.Brieflysummarizetheproposalthenstateheropinionabouttheproposalandexplainthereasonsshegivesforholdingthatopinion.T3FrustrationToleranceWhenyoungchildrenarenotabletoaccomplishtheirgoals,theymaybecomefrustratedandactinappropriately.However,aschildrenmature,theycanlearntomanageortoleratefrustration.Thedevelopmentoffrustrationtoleranceallowschildrentocontinuetoworktowardcompletingtasks,evenwhentheirinitialattemptsareunsuccessful.Parentscanhelptheirchildrendevelopfrustrationtolerancebydeliberatelyrestrictingtheirownresponsestotheirchildren’sdemandsforhelp.Bygraduallyreducingtheirresponsetime,canteachchildrentomanagetheirfrustrationwhiletheykeeptryingtoaccomplishtheirgoals,despiteanydifficultiesorsetbacksthattheymayencounter.Question：Usingtheexamplefromthelecture,explainhowparentscanhelptheirchildrendevelopfrustrationtolerance.T4Question：20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Usingtheexamplesfromthelecture,explaintwotypesofanimalsocialgroups20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題第二部分聽(tīng)力Section1Whydoesthestudentpeakwiththeprofessor?ToaskforassistancecomingupwithanideaforherassignmentTogooveranarticletheprofessorhadassignedTodiscussanarchitecturalconceptshewouldliketoworkwithToreviewherworkonaprojectsherecentlysubmitted.Whatpointdothespeakersmakewhentheydiscussthematerialsusedintheicebergdesign?ThematerialsaredesignedtohelpcoolthebuildingThematerialsaremorecostlythanbuildingmaterialstypicallyusedurbanstructuresThethicknessofmaterialsrequiresthattheybecutwithequipmentD.TheamountofmaterialsusedreducedtheimpactontheenvironmentWhydoestheprofessormentionretailspace?Toexplainthecauseofcitydeveloper’staxproblemTointroducethefocusoftheclass’snextmodelprojectTopointouthowquicklymodernretailstructuresarebuiltToprovidebackgroundonwhytheicebergdesignwascreatedWhatdoestheprofessorsayaboutairbeams?20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Clickon2answersTheyprovidesupporttotheicebergTheyaremadepartlyfromsteelTheypermitanicebergtoassumeavarietyofshapesTheytakealongtimetomanufactureListenagaintopartoftheconversation.Thenanswerthequestion5.Whatcanbeinferredaboutthestudent?Shewasnotfullyawareofthetrip’sdateShedoesnotintendtogoonthetripShehadalreadybeentotheFrankLIoydWrighthouseD.Shewouldtoleadthetour,notbeagroupmember.Whatisthelecturemainlyabout?ThelifeofafamousItalianRenaissanceartistThehistoryoffrescopaintinginItalyThecreationofaparticularworkofRenaissanceartTheconstructionofatypicalchurchoftheItalianRenaissanceAccordingtotheprofessor,whatisoneadvantageofusingthefrescotechnique?AfrescocanlastalongtimeThematerialsformakingafrescoareinexpensiveThefrescotechniqueiseasytolearn20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題AfrescocanbecompletedquicklyAccordingtotheprofessor,whyisafrescopaintedbeforetheplasterdries?A.SothatmistakescanbecorrectedeasilyB.SothatthepaintwillsinkintotheplasterC.SothatthecolorsofthepaintscanbeblendedbetterD.SothathumanformswillappearmorelifelikeWhydoestheprofessormentiontheartistwhopaintedwithapaintbrushineachhand?A.TodescribehowtheSistineChapel’sceilingwaspaintedB.ToillustratetheingeniouscreativityofRenaissanceartistsC.ToexplainhowMichelangelolearnedtopaintD.ToemphasizetheneedforfrescopainterstoworkquicklyWhydidMichelangelochoosetobuildfootbridgesratherthantraditionalscaffoldingwhenhepaintedthechapel?A.Toaccommodatethecurvedshapeofthechapel’sceilingB.TokeepthefloorclearforceremoniesinthechapelC.ToreachboththewallsandtheceilingofthechapelD.TopaintwhilelyingonhisbackforlongperiodsoftimeWhatdoestheprofessorimplywhenhesaysthisHehassuggestionsabouthowstudentscandealwithdifficultsituations20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Manypeoplewouldhavebeenuncomfortablepaintingthechapel’sceilingTherewasoneproblemthatMichelangelowasunabletoovercomeMichelangelo’sreputationasagreatartistmaybesomewhatexaggeratedSection2Whydoesthewomangotoseetheman?ToprovidefeedbackonherprevioushousingexperienceTofindouthowshecanparticipateinadifferenthousingprogramToreapplyforhousingattheEcoHousenextsemesterTogetinformationaboutastudentassistantpositionWhatisthewoman’sattitudeabouttheEcoHouse?A.ShehadhopeditwouldbemorecommittedtosustainablepracticesB.ShebelievesthatitsprogramisexactlywhatshewillneedC.ShethinksitsprogramistoonarrowforheracademicgoalsD.SheregretsthatresidentsareonlypermittedtolivethereforoneyearWhataretwoadvantagesthatlivingattheMaryBlakeClickon2answersA.ItwouldallowhertoactivelyengagewithguestscholarsB.ItwouldallowhertocreateahousethemewithotherstudentsC.ShewouldjoinaclassmatewhocurrentlylivesattheMaryBlakeHouseD.ShewouldhaveanopportunitytoqualifyforstaffdiscountsWhydoesthewomanmentionajournalist?20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題A.ToprovidebackgroundononeofthefacultylivingattheMaryBlakeHouseB.ToprovideanexampleofarecentdinnerguestattheMaryBlakeHouseC.TosuggestawaytocreatepublicityfortheMaryBlakeHouseprogram D.TopointaBlakeHouseprogramguestthatshewouldbeinterestedinWhatdoesthemanaskthewomantodo?FilloutaquestionnaireabouttheMaryBlakeHouseprogramParticipateinareviewofprogramhousesthatisbeingconductedInterviewtobecomeastudentassistantattheEcoHouseProvidefeedbackabouttheapplicationprocessontheWebsiteWhatdoestheprofessormainlydiscuss?ThemainachievementsoftheVoyagerspacecraftmissionDifferencesbetweenUranusandothergasgiantplanetsReasonsfortheincreasinginterestofscientistsintheplanetUranus CharacteristicsofUranuslearnedusingavarietyofmethodsWhydoestheprofessormentionthecolorofUranus?TogiveanexampleofafeaturethatUranusshareswithJupiterTogiveanexampleofadiscoverymadebytheVoyagespacecraftmissionToexplainhowacomponentofUranus’atmospherewasidentified D.explainhowsunlightaffectstemperaturesonUranusAccordingtotheprofessor,howdidastronomersdeducethecompositiontheplanetUranus?20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Clickon2answersBycalculatingUranus’densityBymeasuringUranus’forceofgravityByexaminingthestrengthofUranus’magneticfieldBycomparingUranuswithJupiterWhatfeaturesofUranusdosomeastronomersthinkwerecausedbytheplanet’scollisionwithanotherobject?Clickon2answersThecompositionofitscoreTheangleofitsaxisofrotationItsrapidrotationItslowinternaltemperatureWhydoestheprofessormentionUranus’magneticfield?A.TopointoutasurprisingsimilaritybetweenUranusandEarthB.ToemphasizethelimitationsofremoteobservationsinastronomyC.TopointoutarecentdiscoveryaboutUranusthatcontradictsearlierfindingsD.ToexplainoneeffectofUranus’distancefromtheSunListenagaintopartofthelecture.ThenanswerthequestionWhydoestheprofessorsaythisTosuggestthatthestudent’squestionreflectsacommonmisconceptionToremainthestudentthattheywilldiscussrockyplanetsintheclass.20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題TohelpthestudentrealizetheanswertohisownquestionToencouragethestudenttoclarifywhathemeansWhatisthepurposeofthelectureTosuggestthatcrypticpatternsintheanimalkingdomcanbereducedonlyafewbasicformsToexplainhowcephalopodschangecrypticpatternsbasedontheirperceptionTocontrastunderwateranddrylandcrypsisstrategiesTotracetheevolutionofcrypsisinanimalasadefenseagainstpredatorsWhatcanbeinferredaboutananimalthatonlyusesstipplecrypsis?A.ItwillhaveadifficulttimehidingfrompredatorsB.ItislikelytobeofamediumbodysizeC.ItwilltendtoavoidareaswithmultiplecolorsandpatternsD.ItwillmostlikelybefoundclosetoaseashoreWhathappenstosomecephalopodswhentheyswimoveragravelpatchontheseafloor?A.TheychangetheirskincolortomatchthecolorofthedarkestpiecesofgravelB.TheydisplayirregularlyshapeddarkandlightpatchesC.TheydisplayadisruptivecolorationtomatchthelocalenvironmentD.Theyquicklyswimawayfromthegravelpatch20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Whatfeaturesofdisruptivecrypsisdoestheprofessormention?Clickon2answersA.ItdisguisestheoutlineoftheanimalthatusesitItItworksbycontrastingwiththecolorsinthesurroundinghabitatismosteffectivewhenusedagainstasingle-coloredbackgroundD.ItcanincorporateacombinationofothercrypsispatternsWhydoestheprofessormentionthetiger?ToillustratethatresultsofthecephalopodresearchcanbeextendedmanyotheranimalsTogiveanexampleofananimalwhosecrypsisstrategyhasextensivelystudiedTopointouthowdifferentitscrypsisstrategyisfromthestrategyusedbysmalleranimalsD.ToarguethatpredatorsrelyoncrypsislessthanspeciesdoListentopartofthelecture.ThenanswerthequestionWhatdoestheprofessorimplywhenshesaysthis:CrypsisincephalopodscanrarelyfoolhumanvisualperceptionFewanimalsusecrypsistohidefrompredatorsNewinformationhasledtothereevaluationofsomepreviousassumptionsMorecephalopodresearchneedstobedonetoobtainaccuratedata20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題答案：Section1C D D AC BC A B D B Section2B C （AD）D BD C （AD）（BD）B B C B （AD）A C第三部分寫(xiě)作Argentavismagnificens,thelargestbirdtohaveeverinhabitedEarth,livedsixmillionyearsagointhesouthernpartofSouthAmericathatroughlycorrespondstomodern-dayArgentina.Thebird,whichisknownonlythroughfossilremains,weighedupto68kilograms.Thereissomedebateaboutwhetherthisbirdwasabletoflyorwhetherithadlostitsabilitytoflyatsomepointduringitsevolution.First,thereistheproblemofliftingoffintotheair.Basedonitsskeleton,thebird'stotalwingspanwasnearlysevenmeters.Wingsthislongwouldhavehitthegroundifthebirdhadtriedtoliftofffromastandingposition.Modernflyingbirdshavewing-to-bodyproportionsthatallowthemtotakeoffwithouthittingthegroundwiththeirwings.Second,evenifthebirdhadmanagedtoliftoff,itdoesnotappeartohavehadenoughmusclestrengthtomakecontinuousflightpossible.Aslargeasitwas,theArgentavisdoesnotappeartohavehadsufficientmusclestokeepitshugewingsmoving.Itishighlyimprobablethatitsmusclescouldmoveitswingsfastenoughtokeepitintheairforextendedperiods.20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Third,accordingtothetheoryofevolution,animalsonlyhaveabilitiesthatgivethemanadvantageintheirstruggletosurvive.Flyingwouldnothavegiventhisgiantbirdanyadvantage.Itdidnotneedtoflyinordertoescapepredators,becauseofitssizeithadnopredators.Itcouldnotuseflyingtohuntbecauseitwouldbeensuchaclumsyandinefficientflierthatitcouldnotpossiblyhavecapturedenoughfood.Thebird,therefore,probablylosttheabilitytoflyduringitsevolution.獨(dú)立Doyouagreeordisagreewiththefollowingstatement:Thereisneveragoodreasontobeimpolite(rude)tootherpeople.第四部分閱讀ArtisansinSixteenth-CenturyEuropeForcenturiesEuropeanartisanshadoperatedinsmall,autonomoushandcraftbusinesses,butbythesixteenthcenturyanevolvingeconomicmovingtowardmoderncapitalism,withitsfree-marketpricing,neworganizationofproduction,investments,andsoon—hadstartedtoerodetheirstableandrelativelyprosperousposition.Whatforcescontributedtothedeclineoftheartisan?Inafewindustries,thereappearedtechnologicalinnovationsthatcost20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題moretoinstallandoperatethanartisans—evenassociationsofartisans—couldafford.Forexample,inironproduction,suchspecializedequipmentasblastfurnaces,tilthammers,wiredrawingmachines,andstamping,rolling,andslittingmillsbecamemorefamiliarcomponentsoftheindustry.Thus,theneedforfixedcapital(equipmentandbuildingsusedinproduction)soared.Besidestheseitems,expensiveintheirownright,facilitiesforwater,storage,anddeliverieswereneeded.Inaddition,pig(raw)ironturnedoutbyblastcouldnotbeforgeduntilrefinedfurtherinanewintermediatestage.Inlatesixteenth-centuryAntwerp,whereaskilledworkerearned125to250guildersayear,alargeblastfurnacealonecost3,000guilders,andotherindustrialequipmentwasequallyormoreexpensive.Rawmaterials,notequipment,constitutedartisans’majorexpenseinmosttraders,however.■Whereasin1583anAntwerpsilkweaverpaid12guildersforaloom(andmadesmallpaymentsovermanyyearstopayoffthedebtforpurchasingtheloom),everysixweeksheorshehadtolayout24guildersforthe2poundsofrawsilkrequiredtomakeapieceofcloth. ■Thusaccesstopreoccupationcheapandplentifulprimarymaterialswasaconstant forpreoccupationindependentproducers.■Usinglocalmaterialsmightalloweventhepoorestamongthemtoavoidrelianceonmerchantsuppliers.■Thelossofnearbysourcescouldthereforebedevastating.AssilkcultivationwanedaroundtheSpanishcitiesofCordobaandToledo,weaversinthesecitieswereforcedtobecome20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題employeesofmerchantswhoputoutrawsilkfromValenciaandMurciaprovinces.IntheDutchRepublic,merchantswhoimportedunprocessedsaltfromFrance,Portugal,andSpaingainedcontrolofthesalt-refiningindustryexploitationoflocalsaltmarsheswashaltedforfearthatdikes(whichheldbacktheseafromthelow-lyingDutchland)wouldbeundermined.Credit was necessary for production but created additionalvulnerabilitiesforartisans.Pricesforindustrialproductsthoseofrawmaterialsandfoodstuffs,andthis,coupledwithrisingtaxes,madeitdifficultformanyproducerstorepaytheircreditors.Periodicdownturns,whenfoodpricesshotupanddemandformanufacturesfelloff,drovethemfurtherintodebtorevenintobankruptcy,fromwhichtheymightemergeonlybytoselltheirproductsexclusivelytomerchantsorfellowartisanswhoextendedthemloans.Frequentenoughduringperiodsofgrowth,suchcreditcrisesbecamedeeperandlastedlongerafterabout1570,asdidwar-relateddisruptionsofraw-materialsuppliesandmarkets.Artisans’autonomywasimperiled,too,byrestrictionsontheiraccesstomarkets.Duringthesixteenthcentury,asituationlikethisoftenresultedfromtheconcentrationofexporttradeinafewgreatstorageanddistributioncenters.ThedisappearanceofregionalmarketswhereweaversinFlanders(whatisnownorthernBelgium)hadpreviouslyboughtflaxandsoldlinenleftthematthemercyofbig-citymiddlemen,whoquicklyturnedthemintodomestic20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題workers.Inasimilarfashion,formerlyindependentproducersinsouthernWiltshireinEngland,whohadboughtyarnfromspinnersorlocalbrokersandsoldtheirclothtomerchantsinnearbySalisbury,becamesubjecttoLondonmerchantswhomonopolizedbothwoolsuppliesandwoolensexports.Withgoodreason,finally,urbanartisansfearedthegrowthofindustriesinthecountryside.Foronething,theyworriedthatthespreadofvillagecraftswouldreducetheirsupplyofrawmaterials,drivingupprices.Cityproducersalsoknewthatrurallocationsenjoyedlowerlivingcosts,wages,andtaxes,andoftenemployedfewerorsimplifiedprocesses.Theseadvantagesbecameamajorpreoccupationascompetitionintensifiedinthe1570sand1580s.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.Inthesixteenthcentury,theEuropeaneconomymovedtowardasystemfree-marketpricing,newwaysofproduction,andinvestments.Beforethesixteenthcentury,Europeanmakersofhandcraftsenjoyedstability,autonomy,andrelativeprosperity.Bythesixteenthcentury,theriseofcapitalismbegantoweakentheandrelativeprosperityofEuropeanartisans.Europeanartisansoperatedsmall,autonomousbusinessesbeforecapitalismemergedinthesixteenthcentury.Accordingtoparagraph2,howdidtechnologicaladvancescontributetoeconomicdeclineofartisans?Artisanshadnoplacetostoreorusethenewmachines.Goodsproducedbythenewtechnologywerecheaperthanthoseproducedartisans.Thefixedcostsofremaininginbusinessbecameveryhigh.20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Artisansdidnotknowhowtousethenewmachines.Theword“preoccupation”inthepassageisclosestinmeaningtonecessityconcernstruggleuncertaintyInparagraph3,whydoestheauthorprovidetheinformationaboutanAntwerpsilkweaver’scostsin1583?Todescribesometypicalcostsinthesilk-weavingindustryTosupportthestatementthatartisans’mainexpensewasmaterials,equipmentToargueagainsttheviewthatartisansdidnothavetoborrowmoneytoequipmentToshowthatmaterialswerecheapandplentifulformostartisansAccordingtoparagraph3,whichofthefollowingwassometimesaneffectonartisansofthelossoflocalsourcesoftheirprimarymaterials?Theyhadtoselltheirproductstomerchants.Theyneededtotakeloansinordertobuythematerialsfrommerchants.Theycouldnolongeraffordtobeindependentproducers.□Theyimportedthematerialsfromdistantsources.Accordingtoparagraph4,allofthefollowingcausedeconomicdifficultiesforartisansEXCEPTdecreasingavailabilityofcreditdecreaseddemandformanufacturedgoodsincreasedtaxesproblemscausedbywarsParagraph5supportswhichofthefollowingstatementsaboutartisansduringthesixteenthcentury?Theyhaddifficultytransportingtheirgoodstothebestmarkets.Theywereatadisadvantagebecausetheconcentrationofsuppliesandwasinthehandsofbig-citymerchants.Theyreceivedhigherwagesasemployeesofbig-citymerchants.Theywereabletoobtainrawmaterialsfromlocalmerchants.20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題Allofthefollowingareidentifiedinparagraph6asconcernsthaturbanartisanshadaboutthegrowthofindustryinthecountrysideEXCEPT□adecreaseinthesupplyofrawmaterials□acheapercostoflivinginthecountryside□amoremanageablelevelofcompetitionlesscomplexproductionprocessesinthecountrysideLookatthefoursquares[■]thatindicatewherethefollowingsentencecanbeaddedtothepassage.Thiswaspossiblebecausewhentransportationcostswerelow,thepriceofrawmaterialswasgenerallyalsolow.Wherewouldthesentencebestfit?Clickonasquare[■]toaddthesentencetothepassage.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,onViewText.Europeanartisansexperiencedadeclineduringthesixteenthcenturyasresultofanumberofdevelopments.Europeanartisansexperiencedadeclineduringthesixteenthcenturyasresultofanumberofdevelopments.●●●AnswerchoiceArtisans’abilitytoearnprofitswasrestrictedbytheirdependenceoncreditors,towhomtheywereforcedtoselltheirgoods,andbycompetitionfromruralareas.Asindustriescameunderthecontrolofmerchants,artisanslost20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題accesstocheaprawmaterials,andtheyhadtoborrowmoneytobuythematerialstheyneededfrommerchantsuppliers.Inthenewindustrialsystemfromwhichskilledartisansprogressivelyexcluded,thequalityofmanufactureditemsgraduallydeclined.Advancesintechnologyinsomeindustriesincreasedthecostoftheequipment,buildings,andfacilitiesthatartisansneededforproducingsellingtheirgoods.Ironproductioninthesixteenthcenturydependedonnewinventionssuchasblastfurnaces,tilthammers,wire-drawingmachines,andstamping,rolling,andsiltingmills.Therisingpricesoffoodandothernecessitiesoftenleftartisanswithoutenoughmoneytopaytheirtaxesandotherbusinessexpenses.Earth’sAtmosphereEarth’satmospherehaschangedthroughtime.ComparedtotheSun,whosecompositionisrepresentativeoftherawmaterialsfromwhichEarthandotherplanetsinoursolarsystemformed,Earthcontainslessofsomevolatileelements,suchasnitrogen,argon,hydrogen,andhelium.Theseelementswerelostwhentheenvelopeofgases,orprimaryatmosphere,thatsurroundedearlyEarth,wasstrippedawaybythesolarwindorbymeteoriteimpacts,orboth.Littlebylittle,theplanetgeneratedanew,secondaryatmospherebyvolcanic20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題outgassingofvolatilematerialsfromitsinterior.Volcanicoutgassingcontinuestobethemainprocessbywhichvolatilematerialsarereleasedfromitisnowgoingonatamuchrate.Themainchemicalconstituentofvolcanicgases(asmuchas97percentofvolume)iswatervapor,withvaryingamountsofnitrogen,carbondioxide,andothergases.Infact,thetotalvolumeofvolcanicgasesreleasedoverthepast4billionyearsorsoisbelievedtoaccountforthepresentcompositionoftheatmospherewithoneimportantexception:oxygen.Earthhadvirtuallynooxygeninitsatmospheremorethan4billionyearsago,buttheatmosphereisnowapproximately21percentoxygen.Tracesofoxygenwereprobablygeneratedintheearlyatmospherebythebreakdownofwatermoleculesintooxygenandhydrogenbyultravioletlight(aprocesscalledphotodissociation).Althoughthisisanimportantprocess,itcannotbegintoaccountforthepresenthighlevelsofoxygenintheatmosphere.Almostallofthefreeoxygennowintheatmosphereoriginatedthroughphotosynthesis,theprocesswherebyplantsuselightenergytoinducecarbondioxidetoreactwithwater,producingcarbohydratesandoxygen.Oxygenisaveryreactivechemical,soatfirstmostofthefreeproducedbyphotosynthesiswascombinedwithironinoceanwatertoformironoxide-bearingminerals.Theevidenceofthegradualtransitionfromoxygen-poortooxygen-richwaterispreservedinseafloorsediments.Themineralsin20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題seafloorsedimentaryrocksthataremorethanabout2.5billionyearsoldcontainreduced(oxygen-poor)ironcompounds.Inrocksthatarelessthan1.8billionyearsold,oxidized(oxygen-rich)compoundspredominate.Thesedimentsthatwereprecipitatedduringthetransitioncontainalternatingbandsofred(oxidizediron)andblack(reducediron)minerals.Theserocksarecalledbanded-ironformations.Becauseoceanwaterisinconstantcontactwiththeatmosphere,andthetwosystemsfunctiontogetherinastateofdynamicequilibrium,thetransitionfromanoxygen-poortoanoxygen-richatmospherealsomusthaveoccurredduringthisperiod.Alongwiththebuildupofmolecularoxygen(O2)cameaneventualincreaseinozone(O3)levelsintheatmosphere.■Becauseozonefiltersoutharmfulultravioletradiation,thismadeitpossibleforlifetoflourishinshallowwaterandfinallyonland.■Thiscriticalstateintheevolutionoftheatmospherewasreplacedbetween1100and542millionyears■Interestingly,thefossilrecordshowsanexplosionoflifeforms542millionyearsago.■Oxygenhascontinuedtoplayakeyroleintheevolutionandformoflife.Overthelast200millionyears,theconcentrationofoxygenhasrisenfrom10percenttoasmuchas25percentoftheatmosphere,beforesetting(probablynotpermanently)atitscurrentvalueof21percent.Thisincreasehasbenefited20212021年模擬試題托業(yè)聽(tīng)力閱讀/口語(yǔ)寫(xiě)作考試樣題mammals,whicharevoraciousoxygenconsumers.Notonlydowerequireoxygentofuelourhigh-energy,warm-bloodedmetabolism,ouruniquereproductivesystemdemandsevenmore.Anexpectantmother’sused(venous)bloodmuststillhaveenoughoxygeninittodiffusethroughtheplacentaintoherunbornchild’sbloodstream.Itwouldbeverydifficultforanymammalspeciestosurviveinanatmosphereofonly10percentoxygen.Geologistscannotyetbecertainwhytheatmosphericoxygenlevelsincreased,buttheyhaveahypothesis.First,photosynthesisisonlyonepartoftheoxygencycle.Thecycleiscompletedbydecomposition,inwhichcarboncombineswithoxygenandformscarbondioxide.Butiforganicmatterburiedassedimentbeforeitfullydecomposes,itscarbonisnolongeravailabletoreactwiththefreeoxygen.Thustherewillbeanetaccumulationofcarboninsedimentsandofoxygenintheatmosphere.Inparagraph1,whydoestheauthorstatethatEarthhaslessnitrogen,argon,hydrogen,andheliumthantheSun?Toarguethattheseelementswereoncepartofanearlyatmosphere,disappearedTosuggestthattheseelementsweredrawnintotheSun’satmos