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1、2019-2020年高考英语二轮复习阅读理解训练5阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项中，选出最佳选项。Riversmaybeasignificantsourceofthegreenhousegasnitrousoxide(一氧化二氮),scientistsnowfind.Theircalculationsuggeststhatacrosstheglobethewaterwayscontributethreetimestheamountofnitrousoxidetotheatmosphereashadbeenestim
2、atedbytheInternationalPanelonClimateChange(IPCC),theUnitedNationsscientificbodychargedwithreviewingclimatechangeresearch.Theyfoundthattheamountofnitrousoxideproducedinstreamsisrelatedtohumanactivitiesthatreleasenitrogen(氮)intotheenvironment,suchasfertilizeruseandsewagedisc
3、harges.“Humanactivities,includingfossilfuelbustionandintensiveagriculture,haveincreasedtheavailabilityofnitrogenintheenvironment,”saidJakeBeaulieuoftheUniversityofNotreDameandtheU.S.EnvironmentalProtectionAgencyinCincinnati,Ohio,andleadauthorofthepaperpublishedthisweekinth
4、ejournalProceedingsoftheNationalAcademyofSciences.“Muchofthisnitrogenistransportedintoriverandstreamnetworks,”Beaulieusaid.There,microbes(微生物)convertthenitrogenintonitrousoxide(alsocalledlaughinggas)andaninertgascalleddinitrogen(二氮).Thefindingisimportant,theresearcherssay,
5、becausenitrousoxideisapowerfulgreenhousegasthatcontributestoclimatechangeanddestructionofthestratosphere’sozonelayer,whichprotectsusfromthesun’sharmfulultraviolet(紫外线)radiation.paredwithcarbondioxide,nitrousoxideis300-foldmorepowerfulintermsofitswarmingpotential,thoughcarb
6、ondioxideisafarmoremongreenhousegas.Scientistsestimatenitrousoxideaccountsforabout6percentofhuman-inducedclimatechange.Beaulieuandcolleaguesmeasurednitrousoxideproductionratesin72streams.Whensummedacrosstheglobe,theresultsshowedriversandstreamsarethesourceofatleast10percen
7、tofhuman-causednitrousoxideemissionstotheatmosphere.“Changesinagriculturalandland-usepracticesthatresultinlessnitrogenbeingdeliveredtostreamswouldreducenitrousoxideemissionsfromrivernetworks,”Beaulieusaid.1.Fromthesecondparagraphwecanlearn .A.actuallyriversgiveoffmuchmor
8、enitrousoxidethanexpectedB.scientists’calculationistotallywrongC.humanactivitiesreleaseni
