托福阅读练习4.docx

托福阅读练习4.docx

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托福阅读练习4

Passage1：

Starsmaybespheres,butnoteverycelestialobjectisspherical.Objectsintheuniverseshowavarietyofshapes:

roundplanets（somewithrings）,tailedcomets,

wispycosmicgasanddustclouds,ringednebulae,pinwheel-shapedspiralgalaxies,

Lineandsoon.Butnoneoftheshapesonthislistdescribesthelargestsingleentitiesinthe

（5）universe.Thesearethedoubleradiosources,galaxieswithhugecloudsofradioemission

thatdwarfthevisiblegalaxies,sometimesbyafactorofahundredormore.Stretching

overdistancesgreaterthanamillionlight-years,theseradio-emittingregionsresemble

twinturbulentgasclouds,typicallyformingdumbbell-likeshapeswiththevisible

galaxy（whenitisvisible）inthecenter.

（10）Thesedoubleradiosourcespresentastronomerswithapuzzle.Theirradioemission

arisesfromthesynchrotronprocess,inwhichelectronsacceleratedtonearlythespeed

oflightmovethroughmagneticfields.However,inviewoftherateatwhichtheradio

sourcesemitenergy,theyshoulddisappearinafewmillionyearsastheirelectronsslow

downandcaseproducingradiation.Somehownewelectronsmustbecontinually

（15）acceleratedtonearlythespeedoflight:

otherwise,bynowalmostnoneofthedouble

radiosourceswouldbeobserved.

Withtheadventofhigh-resolutionradiointerferometersduringthelate1970's,part

oftheanswerbecameclear:

theelectronsareproducedinjetsthatareshotoutin

oppositedirectionsfromthecenterofagalaxy.Remarkablynarrowandhighlydirectional,

（20）thejetsmoveoutwardatspeedsclosetothespeedoflight.Whenthejetsstrikethe

highlyrarefiedgasthatpermeatesintergalacticspace,thefast-movingelectronslose

theirhighlydirectionalmotionandformvastcloudsofradio-emittinggas.

Cosmicjetshaverankedamongthehottesttopicsofastronomicalresearchinrecent

yearsasastronomersstrivetounderstandwheretheycomefrom.Whyshouldagalaxy

（25）ejectmatteratsuchtremendousspeedsintwonarrowjets?

Andwhyaresuchjetsnot

seenintheMilkyWay?

1.Theword"celestial"inline1couldbestbe

replacedby

（A）visible

（B）astronomical

（C）glowing

（D）scientific

2.Theword"entities"inline4isclosestin

meaningto

（A）factors（B）processes

（C）objects（D）puzzles

3.Inthefirstparagraph,theauthordescribes

objectsintheuniverseintermsoftheir

（A）color（B）origin

（C）location（D）shape

4.Whichofthefollowingisthebest

representationofthecloudsofradioemission

describedinthefirstparagraph?

（A）

（B）

（C）

（D）

5.Accordingtothepassage,scientistsdonot

fullyunderstandwhydoubleradiosources

（A）havenoteventuallydisappeared

（B）cannotbeobservedwithatelescope

（C）arebeginningtoslowdown

（D）arenotasbigassomeplanetsandstars

6.Theword"their"inline22refersto

（A）speeds

（B）directions

（C）electrons

（D）clouds

7.Accordingtothepassage,whathappenswhen

electronsandgascollideinspace?

（A）Thegasbecomesmorecondensed.

（B）Thegasbecomeslessradiated.

（C）Theelectronsdisperse.

（D）Theelectronsbecomenegativelycharged.

8.Theauthorsuggeststhatastronomersconsider

thestudyofcosmicjetstobe

（A）anobsoletescientificfield

（B）anunprofitableventure

（C）anintriguingchallenge

（D）asubjectivedebate

9.Inwhatlinesdoesthepassagecomparethe

sizeofdoubleradiosourceswiththatofother

galaxies?

（A）Lines4-6（B）Lines12-14

（C）Lines19-20（D）Lines23-24

10.Whereinthepassagedoestheauthormention

atechnologythataidedintheunderstandingof

doubleradiosources?

（A）Lines2（B）Line7

（C）Line17（D）Line21

11.Theparagraphfollowingthepassagemost

likelydiscusses

（A）specificdoubleradiosources

（B）anexplanationofthesynchrotronprocess

（C）possiblereasonsforthepresenceofcosmic

jets

（D）thediscoveryofthefirstdoubleradio

sources

Passage2

Botany,thestudyofplants,occupiesapeculiarpositioninthehistoryofhumanknowledge.

Formanythousandsofyearsitwastheonefieldofawarenessaboutwhichhumanshad

anythingmorethanthevaguestofinsights.ItisimpossibletoknowtodayjustwhatourStone

Ageancestorsknewaboutplants,butfromwhatwecanobserveofpreindustrialsocietiesthat

（5）stillexist,adetailedlearningofplantsandtheirpropertiesmustbeextremelyancient.Thisis

logical.Plantsarethebasisofthefoodpyramidforalllivingthings,evenforotherplants.They

havealwaysbeenenormouslyimportanttothewelfareofpeople,notonlyforfood,butalsofor

clothing,weapons,tools,dyes,medicines,shelter,andagreatmanyotherpurposes.Tribes

livingtodayinthejunglesoftheAmazonrecognizeliterallyhundredsofplantsandknow

（10）manypropertiesofeach.Tothembotany,assuch,hasnonameandisprobablynoteven

recognizedasaspecialbranchof"knowledge"atall.

Unfortunately,themoreindustrializedwebecomethefartherawaywemovefromdirect

contactwithplants,andthelessdistinctourknowledgeofbotanygrows.Yeteveryonecomes

unconsciouslyonanamazingamountofbotanicalknowledge,andfewpeoplewillfailto

（15）recognizearose,anapple,oranorchid.WhenourNeolithicancestors,livingintheMiddle

Eastabout10,000yearsago,discoveredthatcertaingrassescouldbeharvestedandtheirseeds

plantedforricheryieldsthenextseason,thefirstgreatstepinanewassociationofplantsand

humanswastaken.Grainswerediscoveredandfromthemflowedthemarvelofagriculture:

cultivatedcrops.Fromthenon,humanswouldincreasinglytaketheirlivingfromthecontrolled

（20）productionofafewplants,ratherthangettingalittlehereandalittletherefrommanyvarieties

thatgrewwild-andtheaccumulatedknowledgeoflensofthousandsofyearsofexperience

andintimacywithplantsinthewildwouldbegintofadeaway.

12.Whichofthefollowingassumptionsaboutearly

humansisexpressedinthepassage?

（A）Theyprobablyhadextensiveknowledgeof

plants.

（B）Theydividedknowledgeintowell-defined

fields.

（C）Theydidnotenjoythestudyofbotany.

（D）Theyplacedgreatimportanceonownership

ofproperty.

13.Theword"peculiar"inline1isclosestin

meaningto

（A）clear

（B）large

（C）unusual

（D）important

14.Whatdoesthecomment"Thisislogical"in

lines5-6mean?

（A）Thereisnoclearwaytodeterminethe

extentofourancestorsknowledgeofplants.

（B）Itisnotsurprisingthatearlyhumanshada

detailedknowledgeofplants.

（C）Itisreasonabletoassumethatourancestors

behaveverymuchlikepeoplein

preindustrialsocieties.

（D）Humanknowledgeofplantsiswell

organizedandverydetailed.

15.Thephrase"propertiesofeach"inline10refers

toeach

（A）tribe

（B）hundred

（C）plant

（D）purpose

16.Accordingtothepassage,whyhasgeneral

knowledgeofbotanydeclined?

（A）Peoplenolongervalueplantsasauseful

resource.

（B）Botanyisnotrecognizedasaspecialbranch

ofscience.

（C）Researchisunabletokeepupwiththe

increasingnumberofplants.

（D）Directcontactwithavariety,ofplantshas

decreased.

17.Inline15,whatistheauthor'spurposein

mentioning"arose,anapple,oranorchid"?

（A）Tomakethepassagemorepoetic

（B）Tociteexamplesofplantsthatareattractive

（C）Togivebotanicalexamplesthatmostreaders

willrecognize

（D）Toillustratethediversityofbotanicallife

18.Accordingtothepassage,whatwasthefirst

greatsteptowardthepracticeofagriculture?

（A）Theinventionofagriculturalimplements

andmachinery

（B）Thedevelopmentofasystemofnamesfor

plants

（C）Thediscoveryofgrassesthatcouldbe

harvestedandreplanted

（D）Thechangingdietsofearlyhumans

19.Theword"controlled"inline19isclosestin

meaningto

（A）abundant

（B）managed

（C）required

（D）advanced

20.Therelationshipbetweenbotanyandagriculture

issimilartotherelationshipbetweenzoology

（thestudyofanimals）

（A）deerhunting

（B）birdwatching

（C）sheepraising

（D）horsebackriding

21.Whereinthepassagedoestheauthordescribe

thebenefitspeoplederivefromplants?

（A）Line1

（B）Lines6-8

（C）Lines10-11

（D）Lines13-15

PASSAGE3

Ifthephysicalbarriersoftheplantarebreached,thenpreformedchemicalsmayinhibitorkilltheintruder,andplanttissuescontainadiversearrayoftoxicorpotentiallytoxicsubstances,suchasresins,tannins,glycosides,andalkaloids,manyofwhicharehighlyeffectivedeterrentstoinsectsthatfeedonplants.ThesuccessoftheColoradobeetleininfestingpotatoes,forexample,seemstobecorrelatedwithitshightolerancetoalkaloidsthatnormallyrepelpotentialpests.Otherpossiblechemicaldefenses,whilenotdirectlytoxictotheparasite,mayinhibitsomeessentialstepintheestablishmentofaparasiticrelationship.

22.WhichofthefollowingsubstancesdoestheauthormentionasNOTnecessarilybeingtoxictotheColoradobeetle?

（A）Resins

（B）Tannins

（C）Glycosides

（D）Alkaloids

PASSAGE4

Eachpueblorepresentedanastonishingamountofwell-organizedlabor.Usingonlystoneandwoodtools,andwithoutbenefitofwheelsordraftanimals,thebuildersquarriedtonupontonofsandstonefromthecanyonwalls,cutitintosmallblocks,hauledtheblockstotheconstructionsite,andfittedthemtogetherwithmudmortar.Roofbeamsofpineorfirhadtobecarriedfromloggingareasinthemountainforestsmanykilometersaway.Then,toconnectthepueblosandtogiveaccesstothesurroundingtableland,thearchitectslaidoutasystemofpublicroadswithstonestaircasesforascendingcli