英语四级模拟训练题四附答案Word下载.docx
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英语四级模拟训练题四附答案Word下载.docx
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3.鼓励她学好英语。
PartIIReadingComprehension(SkimmingandScanning)
Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswersheet1.
RocketRenaissance
------TheEarofPrivateSpaceflightIsAbouttoStart
Background
Twoyearsago,peoplewitnessedthefirstspacetravelbySpaceShipOne.Threepeoplewereinvolvedinthisflight:
BurtRutan,whodesignedthecraft,andMikeMelvill,whoflewit--althoughtheywereablyassistedbyPaulAllen,oneofthefoundersofMicrosoft,whopaidforit.Certainly,peoplehavelongbeenknownthatmannedspaceflightwaspossible.Whattheyshowedwasthatitisnotjustagameforgovernments.Privateindividualscanplay,too.
Peopleinvolved
Now,lotsofpeoplewanttojoinin,andmostofthemhavejustmetupattheInternationalSpaceDevelopmentConferenceinLosAngeles,toengageinthatmixtureofcamaraderieandcompetitionthatcharacterisesthebeginningsofanewtechnology.And,asmightbeexpected,theyhavetwoofthenecessaryingredientsofsuccess:
ideasandmoney.
First,themoney.Sofar,morethan$1billionisknowntohavebeencommittedtobuildingprivatespaceshipsandtheinfrastructuretosupportthem.Forexample,Mr..Rum'
sfollow-upvehicle,SpaceShipTwo,isexpectedtocostitsbackers,VirginGalactic,$240mforafleetoffive.ThespaceportinNewMexicofromwhichtheseareintendedtoflywillaccountforanother$225m,althoughNewMexico'
sgovernmentisplanningtoraisethismoneyitself.
Thesearenotsmallsums,ofcourse.Ontheotherhand,VirginGalactichasalreadybanked$14mofdepositstowardsthe$200,000farefrompeoplewhowanttotravelonSpaceShipTwo,eventhoughithasyettobebuilt,letaloneflown.
Allthissuggeststhatspaceflight,ifnotexactlyenteringtheageofthecommonman,isatleastenteringtheageofthemoderatelyprosperousenthusiast.Forentrepreneurs,itisnolongernecessarytohavebillionsofdollarstogetintospace;
millionswillnowdo.Andforthosewhomerelywishtotravelthere,andhaveenoughmoneyintheirbankaccount,realityisfavourable.
Getstarted
Aswithaircraftacenturyago,alotofdesignsarecompetingwitheachother,andthereisnocertaintyaboutwhichwillsucceed.Theinitialgoalistobuilda"
suborbital"
vehicle.ThiswillnothavetodevelopthetremendousspeedneededtogointoorbitaroundtheEarth.instead,itwilltravelbrieflyintospace,offeringashortthrillingrideoutoftheatmosphere,afewminutesofweightlessness,andaspectacularviewoftheplanetfromabout100kin.Fourimportantcriteriaarehowyoutakeoff,whatfuelyouuse,whatyourcraftismadeof,andhowyoucomeback.
Mostpeople'
svisionofarocketlaunchisstraightupfromtheground.But,ofthefivevehiclesmostlikelytobedeveloped,twowillactuallybelaunchedfromtheair.SpaceShipTwowillbecardedtohighaltitudebyapurpose-builtaircraftknownasEvebeforeitsrocketmotorisignited.AndExplorer,avehiclebeingdesignedbySpaceAdventures,willbelaunchedfromthetopofahigh-altitudeRussianresearchplanecalledtheM-55X,accordingtoEricAnderson,thefirm'
spresidentandchiefexecutive.
AsDennisJenkins,aconsultantengineeratNASA,America'
sspaceagency,pointsout,thisissimilartousingatwo-stagerockettogetintospace,withtheaircraftactingasthefirststage.However,aplaneoffersseveraladvantagesoverathrow-awayboosterrocket.First,itcanbeusedagain.Second,itusesoxygenfromtheair,ratherthanhavingtocarryitsownoxidant,whichsavesweight.Third,itisliftedbywings.Thatmeanstheatmosphereisanadvantage,ratherthanahindrance.Allthismeansthatthespacecraftitselfcanbelighterandcheaper.
Noteveryonewantstoruntwovehicles,though.JeffGreason,presidentofXCORAerospace,afirmbasedinMojave,California,isdevelopingatwo-person,ground-launchedsuborbitalrocketplanecalledXerus.Launchingfromtheground,saysMr.Greason,ismoredifficultthanairlaunching,buthereckonsthatinthiscaseithassignificantlyloweroperatingcosts.
Fuelchoices
Thesecondimportantdesignchoiceisthetypeoffuel.Unlikeajetengine,arocketcarriesitsownoxidant(氧第剂).Thisiswhyitcanoperateinspace.Sometimesthatoxidantisoxygenitself,inliquidform.Inthatcasethefuel,too,isusuallyliquid-eitherkerosene(煤油)orliquidhydrogen(氢)—andthetwoliquidsarestoredinseparatetanksuntiltheymeetintherocket'
scombustionchamber.Alternatively,bothfuelandoxidantaresolid,andareloadedpre-mixed,likethepropellantofafireworkrocket.
SpaceShipTwo,though,followsthedesignofSpaceShipOneandispoweredbyamixtureofthetwo.Thecombustionchamberofamixtureispartlyfilledwithsolidfuelbutnooxidant.However,thefueliscoatedroundtheinsideofthechamber,leavingaholethroughthemiddleintowhichaliquidorgaseousoxidantcanbepumped,andoutofwhichtheexhaustemerges.InSpaceShipOne,thefuelwasrubberandtheoxidantaliquefiedgascallednitrousoxide(一氧化二氮).
Proponentsofmixturesaytheyaresaferthaneitherpuresolidorpureliquidrockets.GeorgeWhittinghill,VirginGalactic'
schieftechnologist,saysthattheyaresaferthansolidrocketsbecausetheflowofoxidantcanbecontrolled,andcombustionhalted,ifthereisaproblem.Solidrockets,likethefireworkstheyresemble,cannotbestoppeduntiltheyrunoutoffuel.Ontheotherhandliquid-fuelledengines,thoughtheycanbeshutdown,arecomplexandtemperamental.AsMr.Whittinghillobserves,"
theyhavepumps,seals,valvesandlineseverywhere,andthereisalotthatpotentiallycouldgowrong."
Allthisratherirratesthoseworkingonliquidpropulsion.RichardPournelle,headofinvestorrelationsatXCORAerospace,saysthecomparisonisunfair.Liquidpropulsionisroutineinrocketrywhilehybridsarestillrare.Numbersalone,therefore,meanthatliquid-fuelledrocketsblowupmoreoften.That,Mr.Pournelleargues,doesnotprovethattheyareinherentlyunsafe.ChuckLauer,vice-presidentofbusinessdevelopmentforRocketplane,anotherfirmgoingdowntheliquid-fuelledroute,agreesandarguesthatkeroseneiswidelyusedasaviationfuelandnobodycomplainsthatitisunsafe.
1.Itisonlytwoyearsagothatpeoplebecameawareofthefactthatmannedspaceflightwasactuallypossible.
2.Spaceflightispossibleforindividualswhowanttoflyinthespaceandwhohavethemoney.
3.Theinitialgoalofbuildinganaircraftistomakethevehiclefly,andspeedwasnotsuchaprimaryconsideration.
4.Allofthefivevehiclesmostlikelytobedevelopedwillbelaunchedfromtheair.
5.Althoughitispossibletolaunchthespaceshipbothfromgroundandfromtheair,somepeoplebelieveit'
smorecost-effectivetolaunchitfromground.
6.AconsultantengineeratNASApointsoutthatusingaircraftactingasthefirstStageprovidesseveraladvantagesoverathrow-awayboosterrocket.
7.Inthedesignconsiderationsofaspaceship,fuelchoiceisasimportantasthemethodoflaunching.
8.Arocketcarriesitsownoxidant,anditsfuelisusuallyeitherkeroseneor______.
9.Proponentsofmixturesaythattheyare______thaneitherpuresolidorpureliquidrockets.
10.Proponentsofkerosenecitetheexampleof______usingitasfuel
PartⅢListeningComprehension
SectionA
Attheendofeachconversation,oneormorequestionswillbeaskedaboutwhatwassaid.Boththeconversationandthequestionswillbespokenonlyonce.Aftereachquestiontherewillbeapause.Duringthepause,youmustrendthefourchoicesmarked[A]、[B]、[C]and[D],anddecidewhichisthebestanswer.ThenmarkthecorrespondingletteronAnswerSheet2withasinglelinethroughthecentre.
11.[A]Hedidnotknow.[B]Hethoughtitwasverysuccessful.
[C]Hethoughtitwasbad.[D]Hethoughtothersperformbetter.
12.[A]Itwasreportedontheradio.[B]Shereaditinthemorningnews.
[C]Themancalledherimmediately.[D]Shewasintheneighborhood.
13.[A]Playingapiano.[B]Makingaphotocopy.[C]Typing.[D]Takingapicture.
14.[A]Hetalkedwiththeconsultantuntiltwo.[B]Theconsultantwasleavingattwo.
[C]Theconsultantwantedtotalktohim,too.[D]Hecouldn'
ttalktotheconsultantbeforetwo.
15.[A]Themandoesn'
twanttotakeanymorecourses.[B]Thebankneedssomenewemployees.
[C]Thewomansuggeststhatthemangetaloanfromabank.
[D]Themandoesnotknowhowtogetfinancialaids.
16.[A]Better.[B]Tired.[C]Bored.[D]Sick.
17.[A]$160.00.[B]$150.00.[C]$180.00.[D]$120.00.
18.[A]Heisforgetful.[B]Hisclassiseasy.[C]Heislookingforanassistant.[D]Hiscourseisdifficult.
Conversation1
19.[A]Invitethegirltojoinaparty.[B]Invitethegirltogoshopping.
[C]Invitethegirltohavedinner.[D]Invitethegirltowatchamovie.
20.[A]Fromhisfriend.[B]Fromhisneighbor.[C]Fromhisroommate.[D]Fromasponsorofthemovie.
21.[A]Forfree.[B]$50.00apiece.[C]$100.00apiece.[D]Hedidnottellthegirl.
22.[A]Therewillbealotofpeople.[B]Theywillhavedinnertogetherfirst.
[C]Theylivefarfromthetheatre.[D]Therewillbeaheavytraffic.
Conversation2
23.[A]Italy.[B]England.[C]Aus
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