托福模拟题阅读.docx

托福模拟题阅读.docx

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托福模拟题阅读

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（一）

Questions12-20TheelementsotherthanhydrogenandheliumexistInsuchsmallquantitiesthatitisaccuratetosaythattheuniversesomewhatmorethan25percentheliumbyweightandsomewhatlessthan25percenthydrogen.Astronomersh

Questions12-20

　　TheelementsotherthanhydrogenandheliumexistInsuchsmallquantitiesthatitisaccuratetosaythattheuniversesomewhatmorethan25percentheliumbyweightandsomewhatlessthan25percenthydrogen.

　　Astronomershavemeasuredtheabundanceofheliumthroughoutourgalaxyandinothergalaxiesaswell.HeliumhasbeenfoundInoldstars,inrelativelyyoungones,ininterstellargas,andinthedistantobjectsknownasquasars.Heliumnucleihavealsobeenfoundtobeconstituentsofcosmicraysthatfallontheearth（cosmic"rays"arenotreallyaformofradiation;theyconsistofrapidlymovingparticlesofnumerousdifferentkinds）.Itdoesn'tseemtomakeverymuchdifferencewheretheheliumisfound.Itsrelativeabundanceneverseemstovarymuch.Insomeplaces,theremaybeslightlymoreofit;Inothers,slightlyless,buttheratioofheliumtohydrogennucleialwaysremainsaboutthesame.

　　Heliumiscreatedinstars.Infact,nuclearreactionsthatconverthydrogentoheliumareresponsibleformostoftheenergythatstarsproduce.However,theamountofheliumthatcouldhavebeenproducedinthismannercanbecalculated,anditturnsouttobenomorethanafewpercent.Theuniversehasnotexistedlongenoughforthisfiguretohesignificantlygreater.Consequently,iftheuniverseissomewhatmorethan25percentheliumnow,thenitmusthavebeenabout25percentheliumatatimenearthebeginning..

　　However,whentheuniversewaslessthanoneminuteold,noheliumcouldhaveexisted.Calculationsindicatethatbeforethistimetemperaturesweretoohighandparticlesofmatterweremovingaroundmuchtoorapidly.Itwasonlyaftertheone-minutepointthatheliumcouldexist.Bythistime,theuniv

　　ersehadcooledsufficientlythatneutronsandprotonscouldsticktogether.Butthenuclearreactionsthatledtotheformationofheliumwentonforonlyarelativelyshorttime.Bythetimetheuniversewasafewminutesold,heliumproductionhadeffectivelyceased.

　　12.whatdoesthepassagemainlyexplain?

　　（A）Howstarsproduceenergy

　　（B）Thedifferencebetweenheliumandhydrogen

　　（C）Whenmostoftheheliumintheuniversewasformed

　　（D）Whyhydrogenisabundant

　　13.Accordingtothepassage,heliumis

　　（A）thesecond-mostabundantelementintheuniverse

　　（B）difficulttodetect

　　（C）theoldestelementintheuniverse

　　（D）themostprevalentelementinquasars

　　14.Theword"constituents"inline7isclosestinmeaningto

　　（A）relatives　　（B）causes　　（C）ponents　　（D）targets

　　15.Whydoestheauthormention"cosmicrays't'inline7?

　　（A）Aspartofalistofthingscontaininghelium

　　（B）Asanexampleofanunsolvedastronomicalpuzzle

　　（C）Toexplainhowtheuniversebegan

　　（D）Toexplaintheabundanceofhydrogenintheuniverse

　　16.Theword"vary"inline10isclosestillmeaningto

　　（A）mean　　（B）stretch　　（C）change　　（D）include

　　17.Thecreationofheliumwithinstars

　　（A）cannotbemeasured　　（B）producesenergy

　　（C）produceshydrogenasaby-product

　　（D）causesheliumtobemuchmoreabundantInoldstarsthanInyoungstar:

　　18.Theword"calculated"inline15isclosestinmeaningto

　　（A）ignored　　（B）converted　　（C）increased　　（D）determined

　　19.Mostoftheheliumintheuniversewasformed

　　（A）ininterstellarspace　　（B）inaveryshorttime

　　（C）duringthefirstminuteoftheuniverse'sexistence

　　（D）beforemostofthehydrogen

　　20.Theword"ceased"inline26isclosestinmeaningto

（A）extended　　（B）performed　　（C）takenhold　　（D）stopped

HormonesintheBody

　　Uptothebeginningofthetwentiethcentury,thenervoussystemwasthoughttocontrolallmunicationwithinthebodyandtheresultingintegrationofbehavior.Scientistshaddeterminedthatnervesran,essentially,onelectricalimpulses.Theseimpulseswerethoughttobetheengineforthought,emotion,movement,andinternalprocessessuchasdigestion.However,experimentsbyWilliamBaylissandErnestStarlingonthechemicalsecretin,whichisproducedinthesmallintestinewhenfoodentersthestomach,eventuallychallengedthatview.Fromthesmallintestine,secretintravelsthroughthebloodstreamtothepancreas.There,itstimulatesthereleaseofdigestivechemicals.Inthisfashion,theintestinalcellsthatproducesecretinultimatelyregulatetheproductionofdifferentchemicalsinadifferentorgan,thepancreas.

　　Suchacoordinationofprocesseshadbeenthoughttorequirecontrolbythenervoussystem;BaylissandStarlingshowedthatitcouldoccurthroughchemicalsalone.ThisdiscoveryspurredStarlingtocointhetermhormonetorefertosecretin,takingitfromtheGreekwordhormon,meaning“toexcite”or“tosetinmotion.”Ahormoneisachemicalproducedbyonetissuetomakethingshappenelsewhere.

　　Asmorehormoneswerediscovered,theywerecategorized,primarilyaccordingtotheprocessbywhichtheyoperatedonthebody.Someglands（whichmakeuptheendocrinesystem）secretehormonesdirectlyintothebloodstream.Suchglandsincludethethyroidandthepituitary.Theexocrinesystemconsistsoforgansandglandsthatproducesubstancesthatareusedoutsidethebloodstream,primarilyfordigestion.Thepancreasisonesuchorgan,althoughitsecretessomechemicalsintothebloodandthusisalsopartoftheendocrinesystem.

　　Muchhasbeenlearnedabouthormonessincetheirdiscovery.Someplaysuchkeyrolesinregulatingbodilyprocessesorbehaviorthattheirabsencewouldcauseimmediatedeath.Themostabundanthormoneshaveeffectsthatarelessobviouslyurgentbutcanbemorefar-reachinganddifficulttotrack:

Theymodifymoodsandaffecthumanbehavior,evensomebehaviorwenormallythinkofasvoluntary.Hormonalsystemsareveryintricate.Evenminuteamountsoftherightchemicalscansuppressappetite,calmaggression,andchangetheattitudeofaparenttowardachild.Certainhormonesacceleratethedevelopmentofthebody,regulatinggrowthandform;othersmayevendefineanindividual’spersonalitycharacteristics.Thequantitiesandproportionsofhormonesproducedchangewithage,soscientistshavegivenagreatdealofstudytoshiftsintheendocrinesystemovertimeinthehopesofalleviatingailmentsassociatedwithaging.

　　Infact,somehormonetherapiesarealreadyverymon.Abinationofestrogenandprogesteronehasbeenprescribedfordecadestowomenwhowanttoreducemoodswings,suddenchangesinbodytemperature,andotherdisfortscausedbylowernaturallevelsofthosehormonesastheyentermiddleage.Knownashormonereplacementtherapy（HRT）,thetreatmentwasalsobelievedtopreventweakeningofthebones.AtleastonestudyhaslinkedHRTwithaheightenedriskofheartdiseaseandcertaintypesofcancer.HRTmayalsoincreasethelikelihoodthatbloodclots—dangerousbecausetheycouldtravelthroughthebloodstreamandblockmajorbloodvessels—willform.SomeproponentsofHRThavetemperedtheirenthusiasminthefaceofthisnewevidence,remendingitonlytopatientswhosesymptomsinterferewiththeirabilitiestolivenormallives.

　　Humangrowthhormonemayalsobegiventopatientswhoaresecretingabnormallylowamountsontheirown.Becauseoftheplicatedeffectsgrowthhormonehasonthebody,suchtreatmentsaregenerallyrestrictedtochildrenwhowouldbepathologicallysmallinstaturewithoutit.Growthhormoneaffectsnotjustphysicalsizebutalsothedigestionoffoodandtheagingprocess.Researchersandfamilyphysicianstendtoagreethatitisfoolhardytodispenseitincasesinwhichtherisksarenotclearlyoutweighedbythebenefits.

　　27.Thewordengineinthepassageisclosestinmeaningto

　　（A）desire　　（B）origin　　（C）science　　（D）chemical

　　28.Theworditinthepassagerefersto

　　（A）secretin　　（B）smallintestine　　（C）bloodstream　　（D）pancreas

　　29.Thewordspurredinthepassageisclosestinmeaningto

　　（A）remembered　　（B）surprised　　（C）invented　　（D）motivated

　　30.Tobeconsideredahormone,achemicalproducedinthebodymust

　　（A）bepartofthedigestiveprocess

　　（B）influencetheoperationsofthenervoussystem

　　（C）affectprocessesinadifferentpartofthebody

　　（D）regulateattitudesandbehavior

　　31.Theglandsandorgansmentionedinparagraph3arecategorizedaccordingto

　　（A）whetherscientistsunderstandtheirfunction

　　（B）howfrequentlytheyreleasehormonesintothebody

　　（C）whetherthehormonestheysecreteinfluencetheagingprocess

　　（D）whethertheysecretechemicalsintotheblood

　　Paragraph3ismarkedwithanarrow[→]

　　32.Thewordkeyinthepassageisclosestinmeaningto

　　（A）misunderstood　　（B）precise　　（C）significant　　（D）simple

　　33.Thewordminuteinthepassageisclosestinmeaningto

　　（A）sudden　　（B）small　　（C）changing　　（D）noticeable

　　34.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?

Incorrectanswerchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.

　　（A）Mostmoodsandactionsarenotvoluntarybecausetheyareactuallyproducedbytheproductionofhormonesinthebody.

　　（B）Becausetheeffectsofhormonesaredifficulttomeasure,scientistsremainunsurehowfar-reachingtheireffectsonmoodsandactionsare.

　　（C）Whenthebodyisnotproducingenoughhormones,urgenttreatmentmaybenecessarytoavoidpsychologicaldamage.

　　（D）Theinfluenceofmanyhormonesisnoteasytomeasure,buttheycanaffectbothpeople’s