大学英语四级考试Model Test Three.docx

大学英语四级考试Model Test Three.docx

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大学英语四级考试ModelTestThree

大学英语四级考试

ModelTestThree

PartⅠWriting

Directions:

Forthispart,youareallowed30minutestowritealetter.Youshouldwriteatleast120wordsfollowingtheoutlinegivenbelowinChinese:

给你的外国朋友写一封信，告诉他（她）你已经被美国的一所大学录取，但你苦恼的是自己的听力和口语水平不够，你想寻求他（她）对于如何提高听和和口语的建议。

PartⅡReadingComprehension（SkimmingandScanning）

Directions:

Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1.Forquestions1-7,choosethebestanswerfromthefourchoicesmarked[A],[B],[C]and[D].Forquestions8-10,completetilesentenceswiththeinformationgiveninthepassage.

TheEarth

PowerandLight

Comparedtotherestoftheuniverse,theEarthisverysmall.Ourplanetandeight（ormaybenine）othersorbittheSun,whichisonlyoneofabout200billionstarsinourgalaxy.Ourgalaxy,theMilkyWay,ispartoftheuniverse,whichincludesmillionsofothergalaxiesandtheirstarsandplanets.Bycomparison,theEarthismicroscopic.

Comparedtoaperson,ontheotherhand,theEarthisenormous.Ithasadiameterof7,926miles（12,756kilometers）attheequator,andithasamassofabout6×1024kilograms.TheEarthorbitstheSunataspeedofabout66,638milesperhour（29.79kilometerspersecond）.Don'tdwellonthosenumberstoolong,though;toalotofpeople,theEarthisinconceivably,mind-bogglinglybig.Andit'sjustafractionofthesizeoftheSun.

FromourperspectiveonEarth,theSunlooksverysmall.Thisisbecauseit'sabout93millionmilesawayfromus.TheSun'sdiameteratitsequatorisabout100timesbiggerthanEarth's,andaboutamillionEarthscouldfitinsidetheSun.TheSunisinconceivably,mind-bogglinglybigger.

ButwithouttheSun,theEarthcouldnotexist,inasense,theEarthisagiantmachine,fullofmovingpartsandcomplexsystems.Allthosesystemsneedpower,andthatpowercomesfromtheSun.

TheSunisanenormousnuclearpowersource-throughcomplexreactions,ittransformshydrogenintohelium,releasinglightandheat.Becauseofthesereactions,everysquaremeterofourplanet'ssurfacegetsabout342WattsofenergyfromtheSuneveryyear.Thisisabout1.7×1017Wattstotal,orasmuchas1.7billionlargepowerplantscouldgenerate.YoucanlearnabouthowtheSuncreatesenergyinHowtheSunWorks.

WhenthisenergyreachestheEarth,itprovidespowerforavarietyofreactions,cyclesandsystems.Itdrivesthecirculationoftheatmosphereandtheoceans.Itmakesfoodforplants,whichmanypeopleandanimalseat.LifeonEarthcouldnotexistwithouttheSun,andtheplanetitselfwouldnothavedevelopedwithoutit.

Toacasualobserver,theSun'smostvisiblecontributionstolifearelight,heatandweather.

NightandDay

SomeoftheSun'sbiggestimpactsonourplanetarealsoitsmostobvious.AstheEarthspinsonitsaxis,partsoftheplanetareintheSunwhileothersareintheshade.Inotherwords,theSunappearstoriseandset.Thepartsoftheworldthatareindaylightgetwarmerwhilethepartsthataredarkgraduallylosetheheattheyabsorbedduringtheday.

YoucangetasenseofhowmuchtheSunaffectstheEarth'stemperaturebystandingoutsideonapartlycloudyday.WhentheSunisbehindacloud,youfuelnoticeablycoolerthanwhenitisn't.ThesurfaceofourplanetabsorbsthisheatfromtheSunandemitsitthesamewaythatpavementcontinuestogiveoffheatinthesummeraftertheSungoesdown.Ouratmospheredoesthesamethings-itabsorbstheheatthatthegroundemitsandsendssomeofitbacktotheEarth.

TheEarth'srelationshipwiththeSunalsocreatesseasons.TheEarth'saxistipsalittle-about23.5degrees.OnehemispherepointstowardtheSunastheotherpointsaway.ThehemispherethatpointstowardtheSuniswarmerandgetsmorelight--it'ssummerthere,andintheotherhemisphereit'swinter.Thiseffectislessdramaticneartheequatorthanatthepoles,sincetheequatorreceivesaboutthesameamountofsunlightallyear.Thepoles,ontheotherhand,receivenosunlightatallduringtheirwintermonths,whichispartofthereasonwhythey'refrozen.

Mostpeoplearesousedtothedifferencesbetweennightandday（orsummerandwinter）thattheytakethemforgranted.Butthesechangesinlightandtemperaturehaveanenormousimpactonothersystemsonourplanet.Oneisthecirculationofairthroughouratmosphere.Forexample:

TheSunshinesbrightlyovertheequator.TheairgetsverywarmbecausetheequatorfacestheSundirectlyandbecausetheozonelayeristhinnerthere.

Astheairwarms,itbeginstorise,creatingalowpressuresystem.Thehigheritrises,themoretheaircools.Watercondensesastheaircools,creatingcloudsandrainfall.Theairdriesoutastherainfalls.Theresultiswarm,dryair,relativelyhighinouratmosphere.

Becauseofthelowerairpressure,airrushestowardtheequatorfromthenorthandsouth.Asitwarms,itrises,pushingthedryairawaytothenorthandthesouth.

Thedryairsinksasitcools,creatinghigh-pressureareasanddesertstothenorthandsouthoftheequator.

ThisisjustonepieceofhowtheSuncirculatesairaroundtheworld--oceancurrents,weatherpatternsandotherfactorsalsoplayapart.Butingeneral,airmovesfromhigh-pressuretolow-pressureareas,muchthewaythathigh-pressureairrushesfromthemouthofaninflatedballoonwhenyouletgo.Heatalsogenerallymovesfromthewarmerequatortothecoolerpoles.Imagineawarmdrinksittingonyourdesk--theairaroundthedrinkgetswarmerasthedrinkgetscolder.ThishappensonEarthonanenormousscale.

TheCoriolisEffect,aproductoftheEarth'srotation,affectsthissystemaswell.Itcauseslargeweathersystems,likehurricanes,torotate.Ithelpscreatewestward-runningtradewindsneartheequatorandeastward-runningjetstreamsinthenorthernandsouthernhemispheres.Thesewindpatternsmovemoistureandairfromoneplacetoanother,creatingweatherpatterns.（TheCoriolisEffectworksonalargescale--itdoesn'treallyaffectthewaterdrainingfromthesinklikesomepeoplesuppose.）

TheSungetsmuchofthecreditforcreatingbothwindandrain.WhentheSunwarmsairinaspecificlocation,thatairrises,creatinganareaoflowpressure.Moreairrushesinfromsurroundingareastofillthevoid,creatingwind.WithouttheSun,therewouldn'tbewind.Therealsomightnotbebreathableairatall.

WaterandFire

TheSunhasahugeeffectonourwater.Itwarmstheoceansaroundthetropics,anditsabsencecoolsthewateraroundthepoles.Becauseofthis,oceancurrentsmovelargeamountsofwarmandcoldwater,drasticallyaffectingtheweatherandclimatearoundtheworld.TheSunalsodrivesthewatercycle,whichmovesabout18,757cubicmiles（495,000cubickilometers）ofwatervaporthroughtheatmosphereeveryyear.

Ifyou'veevergottenoutofaswimmingpoolonahotdayandrealizedafewminuteslaterthatyouweredryagain,youhavefirsthandexperiencewithevaporation.Ifyou'veseenwaterformonthesideofacolddrink,you'veseencondensationinaction.Theseareprimarycomponentsofthewatercycle,alsocalledthehydrologiccycle,whichexchangesmoisturebetweenbodiesofwaterandlandmasses.Thewatercycleisresponsibleforcloudsandrainaswellasoursupplyofdrinkingwater.

1.HowmanyEarthscouldfitinsidetheSun?

[A]Onemillion.

[B]93million.

[C]Twomillion.

[D]100million.

2.Earthwouldnothavedevelopedwithout______.

[A]water

[B]fertilizer

[C]soil

[D]theSun

3.Whatdoesouratmospheredo?

[A]ItabsorbstheheatfromthegroundandsendsittotheSun.

[B]ItabsorbstheheatfromtheSunandemitsitbacktotheEarth.

[C]ItabsorbstheheatfromtheSunandemitsitthesameway.

[D]ItabsorbstheheatthegroundemitsandsendssomeofitbacktotheEarth.

4.______receivesaboutthesameamountofsunlightallyear.

[A]Thepoles

[B]Theequator

[C]Thenorthtemperatezone

[D]Thesouthtemperatezone

5.Airrushestowardtheequatorfromthenorthandsouth______.

[A]becauseofthedryair

[B]becauseofthecoolair

[C]becauseofthelowerairpressure

[D]becauseofthehigherairpressure

6.Whatdoesn'ttheCoriolisEffectcause?

[A]Westward-runningtradewinds.

[B]Hurricanes.

[C]Thewaterdrainingfromthesink.

[D]Eastward-runningjetstreams.

7.TheSunhascloselyrelationtocreate______.

[A]wind

[B]theair

[C]soil

[D]fire

8.TheSunhasahugeeffecton______.

9.Ifyou'veseenwaterformonthesideofacolddrink,you'veseen______.

10.Thewatercycleisresponsibleforclouds,rainand______.

PartⅢListeningComprehension

SectionA

Directions:

Inthissection,youwillhear8shortconversationsand2longconversations.Attheendofeachconversation,oneormorequestionswillbeaskedaboutwhatwassaid.Boththeconversationandthequestionswillbespokenonlyonce.Aftereachquestiontherewillbeapause.Duringthepause,youmustreadthefourchoicesmarked[A],[B],[C]and[D],anddecidewhichisthebestanswer.ThenmarkthecorrespondingletteronAnswerSheet2withasinglelinethroughthecentre.

Questions11to18arebasedontheconversationyouhavejustheard.

11.[A]Atthedepartmentstore.

[B]Attheoffice.

[C]Intherestaurant.

[D]Inthedrugstore.

12.[A]Themanshouldn'texpecthertogoalong.

[B]Shedoesn'tthinkshehasenoughmoney.

[C]She'llgoeventhoughthemovieisbad.

[D]Themanshouldcountthenumberofpeoplegoing;

13.[A]Shewasn'treallystudying.

[B]Shehadn'tfinishedwritingherarticles.

[C]Shehadfurnishedherhouse.

[D]She