大学英语四级真题4.docx

大学英语四级真题4.docx

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大学英语四级真题4

ModelTestTwo

PartIWriting

Directions:

Forthispart,youareallowed30minutestowriteacompositiononthetopicBridgingtheGapbetweentheUrbanandRuralAreas.Youshouldwriteatleast120words,andbaseyourcompositionontheoutlinegivenbelow:

1.中国城乡之间的差距似乎有增大的趋势

2.导致这种现象的原因

3.怎样才能缩小城乡之间的差距

BridgingtheGapbetweentheUrbanandRuralAreas

__________________________________________________

PartIIReadingComprehension（Skimmingand'Scanning）

Directions:

Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1.Forquestions1—7,choosethebestanswerfromthefourchoicesmarkedA）,B）,C）andD）.Forquestions8—10,completethesentenceswiththeinformationgiveninthepassage.

RadioandTelevision

Radioandtelevisionweremajoragentsofsocialchangeinthe20thcentury.Radiowasoncethecenterforfamilyentertainmentandnewsandtelevisionenhancedthisrevolutionbyaddingsighttosound.Bothopenedthewindowstootherlives,toremoteareasoftheworld,andtohistoryinthemaking.Newscoveragechangedfromearlyandlateeditionsofnewspaperstobroadcastcoveragefromthescene.Play-by-playsportsbroadcastsandliveconcertsenhancedentertainmentcoverage.Formany,theonlyculturalperformancesorsportseventstheywouldeverhearorseewouldcomefromthespeakersorthescreensintheirlivingrooms.Eachhasengagedmillionsofpeopleinthemajorhistoricaleventsthathaveshapedtheworld.

Ifpeoplecouldlookattheskyandseehowitisorganizedintofrequency"bandsusedfordifferentpurposes,theywouldbeamazed.Radiowavescrisscross（十字形）theatmosphereatthespeedoftight,deliveringincredibleamountsofinformation—navigationaldata,radiosignals,televisionpictures—usingdevicesfortransmissionandreceptiondesigned,built,andrefinedbyacenturyofengineers.

Keyfiguresinthelate1800sincludedNikolaTesla,whodevelopedtheTeslacoil,andJamesClerkMaxwellandHeinrichHertz,whoprovedmathematicallythepossibilityoftransmittingelectromagneticsignalsbetweenwidelyseparatedpoints.ItwasGuglielmoMarconiwhowasmostresponsiblefortakingthetheoriesofradiowavesoutofthelaboratoryandapplyingthemtopracticaldevices.His"wireless"telegraphdemonstrateditsgreatpotentialforworldwidecommunicationin1901bysendingasignal—theletter"s"—inMorsecodeadistanceof2000milesacrosstheAtlanticOcean.Radiotechnologywasjustaroundthecomer.

Immediateengineeringchallengesaddressedthemeansoftransmittingandreceivingcodedmessages,anddevelopingadevicethatcouldconvertahigh-frequencyoscillating（振荡的）signalintoanelectriccurrentcapableofregisteringassound.Thefirstsignificantdevelopmentwas"theEdisoneffect",thediscoverythatthecarbonfilament（灯丝）intheelectriclightbulbcouldsendoutastreamofelectronstoanearbytestelectrodeifithadapositivecharge.In1904,SirJohnAmbroseFlemingofBritaintookthisonestepfurtherbydevelopingthediode（二极管）whichallowedelectriccurrenttobedetectedbyatelephonereceiver.Twoyearslater,AmericanLeeDeForestdevelopedthetriode（三极管）,introducingathirdelectrode（thegrid）betweenthefilamentandtheplate.Itcouldamplifyasignaltomakelivevoicebroadcastingpossible,andwasquicklyaddedtoMarconi'swirelesstelegraphtoproducetheradio.

RadiodevelopmentwaspreventedbyrestrictionsplacedonairwavesduringWorldWarI.Technicallimitationswerealsoaproblem.Fewpeoplehadreceivers,andthosethatdidhadtowearheadphones.Radiowasseenbymanyasahobbyfortelegraphyfans.Itwouldtakeagreatdealofengineeringbeforetheradiowouldbecometheunifyingsymboloffamilyentertainmentandthemediumfornewsthatwasitsdestiny.

Inthemid-1920s,technicaldevelopmentsexpandedtransmissiondistances,radiostationswerebuiltacrossthecountry,andtheperformanceandappearanceoftheradiowereimproved.Withtuningcircuits,capacitors,microphones,oscillators,andloudspeakers,theindustryblossomedinjustadecade.Bythemid-1930salmosteveryAmericanhouseholdhadaradio.Theappearanceofthetransistorinthe1950scompletelytransformeditssize,style,andportability.

Bothtelevisionandradarwerelogicalbyproductsoftheradio.Almost50yearsbeforetelevisionbecameareality,itsfundamentalprincipleshadbeenindependentlydevelopedinEurope,Russia,andtheUnitedStates.JohnBairdinEnglandandCharlesJenkinsintheUnitedStatesworkedindependentlytocombinemodulatedlightandascanningwheeltoreconstructascene.In1925,Bairdsucceededintransmittingarecognizableimage.

PhiloT.Farnsworth,a21-year-oldinventorfromUtah,patentedascanningraytube,andVladimirZworykinofRCAdevisedasuperiortelevisioncamerain1930.Regularlyscheduledbroadcastsstartedshortlythereafter,andbytheearly1940stherewere23televisionstationsinoperationthroughouttheUnitedStates.

ShortlyafterWorldWarⅡ,televisionsbegantoappearonthemarket.Thefirstpictureswerefadedandflickering,butmorethanamillionsetsweresoldbeforetheendofthedecade.Anaveragesetcost$500atatimewhentheaveragesalarywaslessthan$3000ayear.In1950engineersperfectedtheprocessofproductionandpricesdroppedto$200perset.Within10years45millionunitsweresold.

Astudyofhowhumanvisionworksenabledengineerstodeveloptelevisiontechnology.Imagesareretainedinaviewer'seyeforonlyafractionofasecondaftertheystrikeit.Bydisplayingimagespiecebypieceatsufficientspeed,theillusionofacompletepicturecanbecreated.Bychangingtheimageonthescreen25to30timespersecond,movementcanberealisticallyrepresented.Earlyscanningwheelsslowlybuiltapicturelinebyline.Incontrast,eachimageonamoderncolortelevisionscreeniscomprisedofmorethan100000pixels（像素）,arrangedinseveralhundredlines.Theimagedisplayedchangeseveryfewhundredthsofasecond.Fora15-minutenewscast,thetelevisionmustaccuratelyprocessmorethan1billionunitsofinformation.Technicalinnovationsthatmadethispossibleincludedascreencoatedwithmillionsoftinydotsoffluorescentcompoundsthatemitlightwhenstruckbyhigh:

speedelectrons.

Todaythistechnologyisintransitionagain,movingawayfromconventionaltelevisionwavesandontoseparatedigitalsignals.Thisholdsthepotentialformakingtelevisioninteractive—allowingaviewertoplayagameororderactionreplays.Cathoderaytubeswithpower-hungryelectrongunsaregivingwaytoliquidcrystaldisplay（LCD）panels.Movie-stylewidescreensandflatscreensarereadilyavailable.DigitalsignalsenableHighDefinitionTelevision（HDTV）tohavealmostdoubledtheusualnumberofpixels,givingamuchsharperpicture.Theappearanceofcabletelevisionandadvancesinfiber-optictechnologywillalsohelpliftthepresentbandwidth（带宽）restrictionsandincreaseimagequality.

1.Themajordifferencebetweenradioandtelevisionis______.

A）whethertheycanbroadcastculturalperformances

B）whethertheymayattractmillionsofpeopleinthegreathistoricalevents

C）whethertheyopenthewindowstoremoteareasoftheworld

D）whethertheymayoffersightstothepeople

2.Whichscientistfirstappliedthetheoriesofradiowavestopracticaldevices?

A）NikolaTesla.B）GuglielmoMarconi.C）ClerkMaxwell.D）HeinrichHertz.

3.Whatdiscoverymadelivevoicebroadcastingbecomeareality?

A）Carbonfilament.B）Diode.C）Triode.D）Wirelesstelegraph.

4.DuringWorldWarI,radio______.

A）wasverypopularamongthepublicB）wasthesymboloffamilyentertainment

C）haddevelopedtoahighlevelD）wasfacingsometechnicalproblems

5.WhendidradiocomeintothecommonAmericanhouseholdinalargescale?

A）IntheWorldWarI.B）Inthemiddleof1920s.

C）Bythemiddleof1930s.D）Inthe1950s.

6.Afterradiohaddevelopedtoaveryhighlevel,whatappearedasanecessaryresult?

A）Televisionandradar.B）Modulatedlightandascanningwheel.

C）Superiortelevisioncamera.D）Microphonesandloudspeakers.

7.Howmanysetsoftelevisionsweresoldinthedecadeof1950?

A）Morethanamillion.B）45million.C）50million.D）100million.

8.Movementcanbeindeedshowedonlyiftheimagesonthescreenarechangedatthefrequencyof______.

9.Televisionwillprobablybecomeinteractiveifthetelevisionwavesarechangedinto______.

10.Presentbandwidthrestrictionsmayberaisedandimagequalitymaybeincreasedwiththehelpof______.

PartIIIListeningComprehension

SectionA

Directions:

Inthissection,youwillhear8shortconversationsand2longconversations.Attheendofeachconversation,oneormorequestionswillbeaskedaboutwhatwassaid.Boththeconversationandthequestionwillbespokenonlyonce.Aftereachquestiontherewillbeapause.Duringthepause,youmustreadthefourchoicesmarkedA）,B）,C）andD）,anddecidewhichisthebestanswer.ThenmarkthecorrespondingletteronAnswerSheet2withasinglelinethroughthecenter.

Questions11to18arebasedontheconversationyouhavejustheard.

11.A）She'drathertakeabreaklater.B）Shelikesthesuggestion.

C）Sheneverdrinkssoda.D）Shedoesn'tthinkheisserious.

12.A）John'sphonewasn'tworking.

B）Johnwasn'tathomewhenshecalled.

C）Thewomandidn'tgettherightphonenumberofJohn's.

D）Johnwastoobusytocome.

13.A）$36.B）$40.C）$100.D）$150.

14.A）Dropoutoftheplay.B）Switchpartswithanotheractor.

C）Bepatientaboutlearninghispart.D）Havehislinesmemorizedbyt