2016年12月英语四级阅读理解备考练习及答案(二)思维导图

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　　Questions 61-65 are based on the following passage. 　　A useful definition of an air pollutantis a compound added directly or indirectly by humans to the atmospherein suchquantit

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2016年12月英语四级阅读理解备考练习及答案(二)思维导图模板大纲

Questions61-65arebasedonthefollowingpassage.

Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindirectlybyhumanstotheatmosphereinsuchquantitiesastoaffecthumans,animals,vegetation,ormaterialadversely(有害地..Airpollutionrequiresaveryflexibledefinitionthatpermitscontinuouschange.WhenthefirstairpollutionlawswereestablishedinEnglandinthefourteenthcentury,airpollutantswerelimitedtocompoundsthatcouldbeseenorsmelled—afarcry(悬殊的差别.fromtheextensivelistofharmfulsubstancesknowntoday.Astechnologyhasdevelopedandknowledgeofthehealthaspectsofvariouschemicalshasincreased,thelistofairpollutantshaslengthened.Inthefuture,evenwatervapor(水蒸气.mightbeconsideredanairpollutantundercertainconditions.

Manyofthemoreimportantairpollutants,suchassulfuroxides,carbonmonoxide,andnitrogenoxides,arefoundinnature.AstheEarthdeveloped,theconcentrations(浓度.ofthesepollutantswerealteredbyvariouschemicalreactions;theybecamecomponentsinbiogeochemical(生物地球化学的.cycles.Theseserveasanairpurificationschemebyallowingthecompoundstomovefromtheairtothewaterorsoil.Onaglobalbasis,nature'soutputofthesecompoundsdwarfsthatresultingfromhumanactivities.However,humanproductionusuallyoccursinalocalizedarea,suchasacity.

Inthislocalizedregion,humanoutputmaybedominantandmaytemporarilyoverloadthenaturalpurificationschemeofthecycles.Theresultisanincreasedconcentrationofnoxious(有害的.chemicalsintheair.Theconcentrationsatwhichtheadverseeffectsappearwillbegreaterthantheconcentrationsthatthepollutantswouldhaveintheabsenceofhumanactivities.Theactualconcentrationneednotbelargeforasubstancetobeapollutant;infactthenumericalvaluetellsuslittleuntilweknowhowmuchofanincreasethisrepresentsovertheconcentrationthatwouldoccurnaturallyinthearea.Forexample,sulfurdioxidehasdetectablehealtheffectsat0.08partspermillion(ppm.,whichisabout400timesitsnaturallevel.Carbonmonoxide,however,hasanaturallevelof0.1ppmandisnotusuallyapollutantuntilitslevelreachesabout15ppm.

61、Itcanbeinferredfromthefirstparagraphthat_________

A.watervaporisanairpollutantinlocalizedareas

B.thedefinitionofairpollutionwillcontinuetochange

C.asubstancebecomesanairpollutantonlyincities

D.mostairpollutantstodaycanbeseenorsmelled

62、Inwhatwaycannaturalpollutantsplayanimportantroleincontrollingairpollution?

A.Theyfunctionaspartofapurificationprocess.

B.Theyaredwarfedbythepollutantsproducedbyhumanactivities.

C.Theyarelessharmfultolivingbeingsthanareotherpollutants.

D.TheyhaveexistedsincetheEarthdeveloped.

63、Accordingtothepassage,thenumericalvalueOftheconcentrationlevelofasubstanceisonlyusefulif

A.theothersubstancesintheareaareknown

B.itisalocalizedarea

C.itcanbecalculatedquickly

D.thenaturallyoccurringlevelisalsoknown

64、Whichofthefollowingisbestsupportedbythepassage?

A.Toeffectivelycontrolpollution,localgovernmentshouldregularlyrevisetheairpollutionlaws.

B.Oneofthemostimportantstepsinpreservingnaturallandsistobetterenforceairpollutionlaws.

C.Scientistsshouldbeconsultedinordertoestablishuniformlimitsforallairpollutants.

D.Humanactivitieshavegreatimpactonairpollution.

65、Thepassagemainlydiscusses_________

A.theeconomicimpactonairpollution

B.howmuchdamageairpollutantscancause

C.whatconstitutesanairpollutant

D.thequantityofcompoundsaddedtotheatmosphere

答案解析：

61-65BADDB

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