托福阅读模拟试题及答案卷八.docx

托福阅读模拟试题及答案卷八.docx

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托福阅读模拟试题及答案卷八

2021年托福阅读模拟试题及答案（卷八）

　　托福阅读文本：

　　Plantsaresubjecttoattackandinfectionbyaremarkablevarietyofsymbioticspeciesandhaveevolvedadiversearrayofmechanismsdesignedtofrustratethepotentialcolonists.Thesecanbedividedintopreformedorpassivedefensemechanismsandinducibleoractivesystems.

　　Passiveplantdefensecomprisesphysicalandchemicalbarriersthatprevententryofpathogens,suchasbacteria,orrendertissuesunpalatableortoxictotheinvader.Theexternalsurfacesofplants,inadditiontobeingcoveredbyanepidermisandawaxycuticle,oftencarryspikyhairsknownastrichomes,whicheitherpreventfeedingbyinsectsormayevenpunctureandkillinsectlarvae.Othertrichomesarestickyandglandularandeffectivelytrapandimmobilizeinsects.

　　Ifthephysicalbarriersoftheplantarebreached,thenpreformedchemicalsmayinhibitorkilltheintruder,andplanttissuescontainadiversearrayoftoxicorpotentiallytoxicsubstances,suchasresins,tannins,glycosides,andalkaloids,manyofwhicharehighlyeffectivedeterrentstoinsectsthatfeedonplants.ThesuccessoftheColoradobeetleininfestingpotatoes,forexample,seemstobecorrelatedwithitshightolerancetoalkaloidsthatnormallyrepelpotentialpests.

　　Otherpossiblechemicaldefenses,whilenotdirectlytoxictotheparasite,mayinhibitsomeessentialstepintheestablishmentofaparasiticrelationship.Forexample,glycoproteinsinplantcellwallsmayinactivateenzymesthatdegradecellwalls.Theseenzymesareoftenproducedbybacteriaandfungi.

　　Activeplantdefensemechanismsarecomparabletotheimmunesystemofvertebrateanimals,althoughthecellularandmolecularbasesarefundamentallydifferent.Both,however,aretriggeredinreactiontointrusion,implyingthatthehosthassomemeansofrecognizingthepresenceofaforeignorganism.Themostdramaticexampleofaninducibleplantdefensereactionisthehypersensitiveresponse.Inthehypersensitiveresponse,cellsundergorapidnecrosis—thatis,theybecomediseasedanddie—afterbeingpenetratedbyaparasite;theparasiteitselfsubsequentlyceasestogrowandisthereforerestrictedtooneorafewcellsaroundtheentrysite.

　　Severaltheorieshavebeenputforwardtoexplainthebasisofhypersensitiveresistance.

　　托福阅读题目：

　　1.Whatdoesthepassagemainlydiscuss?

　　（A）Thesuccessofparasitesinresistingplantdefensemechanisms

　　（B）Theoriesonactiveplantdefensemechanisms

　　（C）Howplantdefensemechanismsfunction

　　（D）Howtheimmunesystemofanimalsandthedefensemechanismsofplantsdiffer

　　2.Thephrase"subjectto"inline1isclosestinmeaningto

　　（A）susceptibleto

　　（B）classifiedby

　　（C）attractiveto

　　（D）strengthenedby

　　3.Theword"puncture"inline8isclosestinmeaningto

　　（A）pierce

　　（B）pinch

　　（C）surround

　　（D）cover.

　　4.Theword"which"inline12refersto

　　（A）tissues

　　（B）substances

　　（C）barriers

　　（D）insects

　　5.WhichofthefollowingsubstancesdoestheauthormentionasNOTnecessarilybeingtoxicto

　　theColoradobeetle?

　　（A）resins

　　（B）tannins

　　（C）glycosides

　　（D）alkaloids

　　6.Whydoestheauthormention"glycoproteins"inline17?

　　（A）tocompareplantdefensemechanismstotheimmunesystemofanimals

　　（B）tointroducethediscussionofactivedefensemechanismsinplants

　　（C）toillustratehowchemicalsfunctioninplantdefense

　　（D）toemphasizetheimportanceofphysicalbarriersinplantdefense

　　7.Theword"dramatic"inline23couldbestbereplacedby

　　（A）striking

　　（B）accurate

　　（C）consistent

　　（D）appealing

　　8.Whereinthepassagedoestheauthordescribeanactiveplant-defensereaction?

　　（A）Lines1-3

　　（B）Lines4-6

　　（C）Lines13-15

　　（D）Lines24-27

　　9.Thepassagemostprobablycontinueswithadiscussionoftheorieson

　　（A）thebasisofpassiveplantdefense

　　（B）howchemicalsinhibitaparasiticrelationship.

　　（C）howplantsproducetoxicchemicals

　　（D）theprinciplesofthehypersensitiveresponse.

　　托福阅读答案：

　　CAABDCADD

　　托福阅读文本：

　　Anyrockthathascooledandsolidifiedfromamoltenstateisanigneousrock.Therefore,iftheEarthbeganasasuperheatedsphereinspace,alltherocksmakingupitscrustmaywellhavebeenigneousandthustheancestorsofallotherrocks.Eventoday,approximately95percentoftheentirecrustisigneous.Periodically,moltenmaterialwellsoutoftheEarth'sinteriortoinvadethesurfacelayersortoflowontothesurfaceitself.Thismaterialcoolsintoawidevarietyofigneousrocks.Inthemoltenstate,itiscalledmagmaasitpushesintothecrustandlavawhenitrunsoutontothesurface.

　　Allmagmaconsistsbasicallyofavarietyofsilicateminerals（highinsilicon-oxygencompounds）,butthechemicalcompositionofanygivenflowmaydifferradicallyfromthatofanyother.Theresultingigneousrockswillreflectthesedifferences.Igneousrocksalsovaryintextureaswellaschemistry.Granite,forinstance,isacoarse-grainedigneousrockwhoseindividualmineralcrystalshaveformedtoasizeeasilyseenbythenakedeye.Aslowrateofcoolinghasallowedthecrystalstoreachthissize.Normally,slowcoolingoccurswhenthecrustisinvadedbymagmathatremainsburiedwellbelowthesurface.Granitemaybefoundonthesurfaceofthecontemporarylandscape,butfromitscoarsetextureweknowthatitmusthaveformedthroughslowcoolingatagreatdepthandlaterbeenlaidbarebyerosion.Igneousrockswiththiscoarse-grainedtexturethatformedatdeptharecalledplutonic.

　　Ontheotherhand,ifthesamemagmaflowsontothesurfaceandisquicklycooledbytheatmosphere,theresultingrockwillbefine-grainedandappearquitedifferentfromgranite,althoughthechemicalcompositionwillbeidentical.Thiskindofrockiscalledrhyolite.Themostfinelygrainedigneousrockisvolcanicglassorobsidian,whichhasnocrystals.Someresearchersbelievethisisbecauseofrapidcooling;othersbelieveitisbecauseofalackofwatervaporandothergasesinthelava.TheblackobsidiancliffsofYellowstoneNationalParkaretheresultofalavaflowofbasaltrunningheadonintoaglacier.Someoftheglaciermeltedoncontact,butsuddenlytherealsoappearedahugeblackmassofglassystone.

　　托福阅读题目：

　　1.Inthefirstparagraph,theauthormentionsthat95%oftheEarth'scrustiscomposedofigneousrocktosupporttheideathat

　　（A）theEarthbeganasamoltenmass

　　（B）athinlayerofmagmaflowsbeneaththeEarth'scrust

　　（C）themineralsfoundinigneousrockareverycommon

　　（D）igneousrockiscontinuallybeingformed

　　2.Theword"invade"inline5isclosestinmeaningto

　　（A）moveinto

　　（B）neutralize

　　（C）cover

　　（D）deposit

　　3.Theword"contemporary"inline15isclosestinmeaningto

　　（A）vast

　　（B）natural

　　（C）existing

　　（D）uneven

　　4.Theword"it"inline16refersto

　　（A）granite

　　（B）surface

　　（C）landscape

　　（D）texture

　　5.Granitethathasbeenfoundabovegroundhasbeen

　　（A）pushedupfrombelowthecrustbymagma

　　（B）producedduringavolcanicexplosion

　　（C）graduallyexposedduetoerosion

　　（D）pushedupbythenaturalshiftingoftheEarth

　　6.Whichofthefollowingisproducedwhenmagmacoolsrapidly?

　　（A）granite

　　（B）plutonicrock

　　（C）rhyolite

　　（D）mineralcrystals

　　7.Theword"finely"inline22isclosestinmeaningto

　　（A）minutely

　　（B）loosely

　　（C）sensitively

　　（D）purely

　　8.Whichofthefollowingisanothernameforvolcanicglass?

　　（A）Plutonicrock

　　（B）Crystal

　　（C）Lava

　　（D）Obsidian

　　托福阅读答案：

　　AACACCAD

　　托福阅读文本：

　　TelevisionhastransformedpoliticsintheUnitedStatesbychangingthewayinwhichinformationisdisseminated,byalteringpoliticalcampaigns,andbychangingcitizen'spatternsofresponsetopolitics.Bygivingcitizensindependentaccesstothecandidates,televisiondiminishedtheroleofthepoliticalpartyintheselectionofthemajorpartycandidates.Bycenteringpoliticsonthepersonofthecandidate,televisionacceleratedthecitizen'sfocusoncharacterratherthanissues.

　　Televisionhasalteredtheformsofpoliticalcommunicationaswell.Themessagesonwhichmostofusrelyarebrieferthantheyoncewere.Thestumpspeech,apoliticalspeechgivenbytravelingpoliticiansandlasting11/2to2hours,whichcharacterizednineteenth-centurypoliticaldiscourse,hasgivenwaytothe30-secondadvertisementandthe10second"soundbite"inbroadcastnews.Increasinglytheaudienceforspeechesisnotthatstandinginfrontofthepoliticianbutrathertheviewingaudiencewhowillhearandseeasnippetofthespeechonthenews.

　　Intheseabbreviatedforms,muchofwhatconstitutedthetraditionalpoliticaldiscourseofearlierageshasbeenlost.In15or30seconds,aspeakercannotestablishthehistoricalcontextthatshapedtheissueinquestion,cannotdetailtheprobablecausesoftheproblem,andcannotexaminealternativeproposalstoarguethatoneispreferabletoothers.Insnippets,politiciansassertbutdonotargue.

　　Becausetelevisionisanintimatemedium,speakingthroughitrequireachangedpoliticalstylethatwasmoreconversational,personal,andvisualthanthatoftheold-stylestumpspeech.Relianceontelevisionmeansthatincreasinglyourpoliticalworldcontainsmemorablepicturesratherthanmemorablewords.Schoolsteachustoanalyzewordsandprint.However,inawordinwhichpoliticsisincreasinglyvisual,informedcitizenshiprequiresanewsetofskills.

　　Recognizingthepoweroftelevision'spictures,politicianscrafttelevisual,stagedevents,calledpseudo-event,designedtoattractmediacoverage.Muchofthepoliticalactivityweseeontelevi