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SAMPLE18

[环境科学类]

题目序号题型归类

第1题中心主旨题型

第2题指代词题型

第3题审题定位与中心主旨题型

第4题类比题型

第5题细节推导题型

Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutantsfromindividualmotorvehicles,thenumberofsuchvehicleshasbeensteadilyincreasing.Consequently,morethan100citiesintheUnitedStatesstillhavelevelsofcarbonmonoxide,particulatematter,andozone(generatedbyphotochemicalreactionswithhydrocarbonsfromvehicleexhaust)thatexceedlegallyestablishedlimits.Thereisagrowingrealizationthattheonlyeffectivewaytoachievefurtherreductionsinvehicleemissions—shortofamassiveshiftawayfromtheprivateautomobile—istoreplaceconventionaldieselfuelandgasolinewithcleaner-burningfuelssuchascompressednaturalgas,liquefiedpetroleumgas,ethanol,ormethanol.

Allofthesealternativesarecarbon-basedfuelswhosemoleculesaresmallerandsimplerthanthoseofgasoline.Thesemoleculesburnmorecleanlythangasoline,inpartbecausetheyhavefewer,ifany,carbon-carbonbondsandthehydrocarbonstheydoemitarelesslikelytogenerateozone.Thecombustionoflargermolecules,whichhavemultiplecarbon-carbonbondsinvolvesamorecomplexseriesofreactions.Thesereactionsincreasetheprobabilityofincompletecombustionandaremorelikelytoreleaseuncombustedandphotochemicallyactivehydrocarboncompoundsintotheatmosphere.Ontheotherhand,alternativefuelsdohavedrawbacks.Compressednaturalgaswouldrequirethatvehicleshavesetofheavyfueltanks—aseriousliabilityintermsofperformanceandfuelefficiency—andliquefiedpetroleumgasfacesfundamentallimitsonsupply.

Ethanolandmethanol,ontheotherhand,haveimportantadvantagesoverothercarbon-basedalternativefuels:theyhavehigherenergycontentpervolumeandwouldrequireminimalchangesintheexistingnetworkfordistributingmotorfuel.Ethanoliscommonlyusedasagasolinesupplement,butitiscurrentlyabouttwiceasexpensiveasmethanol,thelowcostofwhichisoneofitsattractivefeatures.Methanol’smostattractivefeature,however,isthatitcanreducebyabout90percentthevehicleemissionsthatformozone,themostseriousurbanairpollutant.

Likeanyalternativefuel,methanolhasitscritics.Yetmuchofthecriticismisbasedontheuseof“gasolineclone”vehiclesthatdonotincorporateeventhesimplestdesignimprovementsthataremadepossiblewiththeuseofmethanol.Itistrue,forexample,thatagivenvolumeofmethanolprovidesonlyaboutone-halfoftheenergythatgasolineanddieselfueldo;otherthingsbeingequal,thefueltankwouldhavetobesomewhatlargerandheavier.However,sincemethanol-fueledvehiclescouldbedesignedtobemuchmoreefficientthan“gasolineclone”vehiclesfueledwithmethanoltheywouldneedcomparativelylessfuel.Vehiclesincorporatingonlythesimplestoftheengineimprovementsthatmethanolmakesfeasiblewouldstillcontributetoanimmediatelesseningofurbanairpollution.

1.Theauthorofthetextisprimarilyconcernedwith

[A]counteringaflawedargumentthatdismissesapossiblesolutiontoaproblem.

[B]reconcilingcontradictorypointsofviewaboutthenatureofaproblem.

[C]identifyingthestrengthsofpossiblesolutionstoaproblem.

[D]discussingaproblemandarguinginfavorofonesolutiontoit.

2.Accordingtothetext,incompletecombustionismorelikelytooccurwithgasolinethanwithanalternativefuelbecause

[A]thecombustionofgasolinereleasesphotochemicallyactivehydrocarbons.

[B]thecombustionofgasolineembracesanintricatesetofreactions.

[C]gasolinemoleculeshaveasimplemolecularstructure.

[D]gasolineiscomposedofsmallmolecules.

3.Thetextsuggestswhichofthefollowingaboutairpollution?

[A]Furtherattemptstoreduceemissionsfromgasoline-fueledvehicleswillnothelplowerurbanair-pollutionlevels.

[B]Attemptstoreducethepollutantsthatanindividualgasoline-fueledvehicleemitshavebeenlargelyunsuccessful.

[C]Fewseriousattemptshavebeenmadetoreducetheamountofpollutantsemittedbygasoline-fueledvehicles.

[D]Pollutantsemittedbygasoline-fueledvehiclesarenotthemostcriticalsourceofurbanairpollution.

4.Whichofthefollowingmostcloselyparallelsthesituationdescribedinthefirstsentenceofthetext?

[A]Althoughatownreducesitspublicservicesinordertoavoidataxincrease,thetown’staxrateexceedsthatofothertownsinthesurroundingarea.

[B]Althoughastatepassesstrictlawstolimitthetypeoftoxicmaterialthatcanbedisposedofinpubliclandfills,illegaldumpingcontinuestoincrease.

[C]Althoughatown’scitizensreducetheirindividualuseofwater,thetown’swatersuppliescontinuetodwindlebecauseofasteadyincreaseinthetotalpopulatingofthetown.

[D]Althoughacountryattemptstoincreasethesaleofdomesticgoodsbyaddingataxtothepriceofimportedgoods,thesaleofimportedgoodswithinthecountrycontinuestoincrease.

5.Itcanbeinferredthattheauthorofthetextmostlikelyregardsthecriticismofmethanolas

[A]flawedbecauseoftheassumptionsonwhichitisbased.

[B]inapplicablebecauseofaninconsistencyinthecritics’arguments.

[C]misguidedbecauseofitsexclusivelytechnologicalfocus.

[D]inaccuratebecauseitignoresconsumers’concerns.