大学英语四级模拟试题及答题详解Word格式.docx

大学英语四级模拟试题及答题详解Word格式.docx

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　　NG（forNOTGIVEN）iftheinformationisnotgiveninthepassage.

　　Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage.

　　Sleep

　　Sleepisoneofthosefunnythingsaboutbeingahumanbeing---youjusthavetodoit.Haveyoueverwonderedwhy?

Andwhataboutthecrazydreams,liketheonewhereabadpersonischasingyouandyoucan’trunoryell.Doesthatmakeanysense?

　　CharacteristicsofSleep

　　Whenweseesomeonesleeping,werecognizethefollowingcharacteristics:

　　Ifpossible,thepersonwillliedowntogotosleep.

　　Theperson’seyesareclosed.

　　Thepersondoesn’thearanythingunlessitisaloudnoise.

　　Thepersonbreathesinaslow,rhythmicpattern.

　　Theperson’smusclesarecompletelyrelaxed.Ifsittingup,thepersonmayfalloutofhisorherchairassleepdeepens.

　　Duringsleep,thepersonoccasionallyrollsoverorrearrangeshisorherbody.Thishappensapproximatelyonceortwiceanhour.Thismaybethebody’swayofmakingsurethatnopartofthebodyorskinhasitscirculationcutofffortoolongaperiodoftime.

　　Inadditiontotheseoutwardsigns,theheartslowsdownandthebraindoessomeprettyfunkythings.

　　Inotherwords,asleepingpersonisunconscioustomostthingshappeningintheenvironment.Thebiggestdifferencebetweensomeonewhoisasleepandsomeonewhohasfaintedorgoneintoacomaisthefactthatasleepingpersoncanbearousedifthestimuluspresentedbyisstrongenough.Ifyoushaketheperson,yellloudlyorflashabrightlight,asleepingpersonwillwakeup.

　　WhoSleeps?

　　Reptiles（爬行动物），birdsandmammalsallsleep.Thatis,theybecomeunconscioustotheirsurroundingsforperiodsoftime.Somefishandamphibians（两栖动物）reducetheirawarenessbutdonoteverbecomeunconsciouslikethehighervertebrates（脊椎动物）do.Insectsdonotappeartosleep,althoughtheymaybecomeinactiveindaylightordarkness.

Bystudyingbrainwaves,itisknownthatreptilesdonotdream.Birdsdreamalittle.Mammalsalldreamduringsleep.

　　Differentanimalssleepindifferentways.Someanimals,likehumans,prefertosleepinonelongsession.Otheranimalsliketosleepinmanyshortbursts.Somesleepatnight,whileotherssleepduringtheday.

　　SleepandtheBrain

　　Ifyouattachanelectroencephalographtoaperson’shead,youcanrecordtheperson’sbrainwaveactivity.Anawakeandrelaxedpersongeneratesalphawaves,whichareconsistentoscillationsatabout10cyclespersecond.Analertpersongeneratesbetawaves,whichareabouttwiceasfast.

　　Duringsleep,twoslowerpatternscalledthetawavesanddeltawavestakeover.Thetawaveshaveoscillationsintherangeof3.5to7cyclespersecond,anddeltawaveshaveoscillationsoflessthan3.5cyclespersecond.Asapersonfallsasleepandsleepdeepens,thebrainwavepatternsslowdown.Apersondeepindeltawavesleepishardesttowakeup.

　　REMSleep

　　Atseveralpointsduringthenight,somethingunexpectedhappens--rapideyemovement（REM）sleepoccurs.MostpeopleexperiencethreetofiveintervalsofREMsleeppernight,andbrainwavesduringthisperiodspeeduptoawakelevels.IfyoueverwatchapersonoradogexperiencingREMsleep,youwillseetheireyesflickeringbackandforthrapidly.Inmanydogsandsomepeople,arms,legsandfacialmuscleswilltwitchduringREMsleep.PeriodsofsleepotherthanREMsleepareknownasNREM（non-REM）sleep.

　　REMsleepiswhenyoudream.IfyouwakeupapersonduringREMsleep,thepersoncanvividlyrecalldreams.IfyouwakeupapersonduringNREMsleep,generallythepersonwillnotbedreaming.

　　YoumusthavebothREMandNREMsleeptogetagoodnight’ssleep.Anormalpersonwillspendabout25percentofthenightinREMsleep,andtherestinNREM.AREMsessionadream--lastsfiveto30minutes.

　　WhenYouMissSomeZzzzs…

　　Onewaytounderstandwhywesleepistolookatwhathappenswhenwedon’tgetenough:

Asyouknowifyouhaveeverpulledanall-nighter,missingonenightofsleepisnotfatal.Apersonwillgenerallybeirritableduringthenextdayandwilleitherslowdown（becometiredeasily）orwillbetotallywiredbecauseofadrenalin（肾上腺素）。

　　Ifapersonmissestwonightsofsleep,itgetsworse.Concentrationisdifficult,andattentionspanfallsbythewayside.Mistakesincrease.

　　Afterthreedays,apersonwillstarttohallucinateandclearthinkingisimpossible.Withcontinuedwakefulnessapersoncanlosegraspofreality.Ratsforcedtostayawakecontinuouslywilleventuallydie,provingthatsleepisessential.

　　Apersonwhogetsjustafewhoursofsleeppernightcanexperiencemanyofthesameproblemsovertime.

　　Twootherthingsareknowntohappenduringsleep.Growthhormoneinchildrenissecretedduringsleep,andchemicalsimportanttotheimmunesystemaresecretedduringsleep.Youcanbecomemorepronetodiseaseifyoudon’tgetenoughsleep,andachild’sgrowthcanbestunted（阻碍）bysleepdeprivation.

　　WhySleep?

　　Noonereallyknowswhywesleep.But,thereareallkindsoftheories,includingthese:

Sleepgivesthebodyachancetorepairmusclesandothertissues,replaceagingordeadcells,etc.

　　Sleepgivesthebrainachancetoorganizeandarchivememories.Dreamsarethoughtbysometobepartofthisprocess.

Sleeplowersourenergyconsumption,soweneedthreemealsadayratherthanfourorfive.Sincewecan’tdoanythinginthedarkanyway,wemightaswell"

turnoff"

andsavetheenergy.

　　Whatweallknowisthat,withagoodnight’ssleep,everythinglooksandfeelsbetterinthemorning.Boththebrainandthebodyarerefreshedandreadyforanewday.

　　Dreams

　　Thebraincreatesdreamsthroughrandomelectricalactivity.Randomisthekeywordhere.Aboutevery90minutesthebrainstemsendselectricalimpulsesthroughoutthebrain,innoparticularorderorfashion.Theanalyticportionofthebrain--theforebrain----thendesperatelytriestomakesenseofthesesignals.ItislikelookingataRorschachtest,arandomsplashofinkonpaper.Theonlywayofcomprehendingitisbyviewingthedream（ortheinkblot）metaphorically,symbolically,sincethere’snoliteralmessage.

　　Thisdoesn’tmeanthatdreamsaremeaninglessorshouldbeignored.Howourforebrainschooseto"

analyze"

therandomanddiscontinuousimagesmaytellussomethingaboutourselves,justaswhatweseeinaninkblotcanberevelatory.Andperhapsthereisapurposetothecraziness:

Ourmindsmaybeworkingondeep-seatedproblemsthroughthesecircuitousandlessthreateningmetaphoricaldreams.

　　Herearesomeotherthingsyoumayhavenoticedaboutyourdreams:

　　Dreamstellastory.TheyarelikeaTVshow,withscenes,charactersandprops.

　　Dreamsareegocentric.Theyalmostalwaysinvolveyou.

　　Dreamsincorporatethingsthathavehappenedtoyourecently.Theycanalsoincorporate

　　deepwishesandfears.

　　Anoiseintheenvironmentisoftenworkedintoadreaminsomeway,givingsomecredibilitytotheideathatdreamsaresimplythebrain’sresponsetorandomimpulses.

　　Youusuallycannotcontroladream--infact,manydreamsemphasizeyourlackofcontrolbymakingitimpossibletorunoryell.

　　Dreamingisimportant.Insleepexperimentswhereapersoniswokenupeverytimehe/sheentersREMsleep,thepersonbecomesincreasinglyimpatientanduncomfortableovertime.

　　HowMuchSleepDoINeed?

　　Mostadultpeopleseemtoneedseventoninehoursofsleepanight.Thisisanaverage,anditisalsosubjective.You,forexample,probablyknowhowmuchsleepyouneedinanaveragenighttofeelyourbest.

　　Theamountofsleepyouneeddecreaseswithage.Anewbornbabymightsleep20hoursaday.Byagefour,theaverageis12hoursaday.Byage10,theaveragefallsto10hoursaday.Seniorcitizenscanoftengetbywithsixorsevenhoursaday.

　　1.Thispassagetellsuswhypeoplehavetosleepandwhatcausesdreams.

　　2.Duringsleep,thepersonisconscioustomostthingshappeningintheenvironment.

　　3.Neitherreptilesnorbirdsdreamduringsleep.

　　4.AnormalpersonspendsthemainpartofthenightinNREMsleep.

　　5.Ifyoumissonenightofsleep,youwillloseyourappetitetosomeextent.

　　6.Nobodyreallyknowsthereasonwhywesleep.

　　7.Generallyspeaking,youneedlessamountofsleepasyougrowolder.

8.Theslower,thedeeperthesleep.

　　9.REMinthispassagestandsfor________________________.

　　10.Thebrainstemsendselectricalimpulsesthroughoutthebrainaboutevery________________

　　PartIVReadingComprehension（ReadinginDepth）（25minutes）

　　SectionA

Inthissection,thereisapassagewithtenblanks.Youarerequiredtoselectonewordforeachblankfromalistofchoicesgiveninawordbankfollowingthepassage.Readthepassagethroughcarefullybeforemakingyourchoices.Eachchoiceinthebankisidentifiedbyaletter.PleasemarkthecorrespondingletterforeachitemonAnswerSheet2withasinglelinethroughthecentre.Youmaynotuseanyofthewordsinthebankmorethanonce.

　　Questions47to56arebasedonthefollowingpassage.