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Questions21to25arebasedonthefollowingpassage.Leaddeposits,whichaccumulatedinsoilandsnowduringthe1960’sand70’s,wereprimarilytheresultofleadedgasolineemissionsoriginatingintheUnitedStates.InthetwentyyearsthattheCleanAirActhasmandatedunleadedgasuseintheUnitedStates,theleadaccumulationworldwidehasdecreasedsignificantly.AstudypublishedrecentlyinthejournalNatureshowsthatair-borneleadedgasemissionsfromtheUnitedStatesweretheleadingcontributortothehighconcentrationofleadinthesnowinGreenland.ThenewstudyisaresultofthecontinuedresearchledbyDr.CharlesBoutron,anexpertontheimpactofheavymetalsontheenvironmentattheNationalCenterforScientificResearchinFrance.AstudybyDr.Boutronpublishedin1991showedthatleadlevelsinarctic(北极的)snowweredeclining.Inhisnewstudy,Dr.BoutronfoundtheratiosofthedifferentformsofleadintheleadedgasolineusedintheUnitedStatesweredifferentfromtheratiosofEuropean,AsianandCanadiangasolinesandthusenabledscientiststodifferentiate(区分)theleadsources.ThedominantleadratiofoundinGreenlandsnowmatchedthatfoundingasolinefromtheUnitedStates.InastudypublishedinthejournalAmbio,scientistsfoundthatleadlevelsinsoilintheNortheasternUnitedStateshaddecreasedmarkedlysincetheintroductionofunleadedgasoline.Manyscientistshadbelievedthattheleadwouldstayinsoilandsnowforalongerperiod.TheauthorsoftheAmbiostudyexaminedsamplesoftheupperlayersofsoiltakenfromthesamesitesof30forestfloorsinNewEngland,NewYorkandPennsylvaniain1980andin1990.Theforestenvironmentprocessedandredistributedtheleadfasterthanthescientistshadexpected.Scientistssaybothstudiesdemonstratethatcertainpartsoftheecosystem(生态系统)respondrapidlytoreductionsinatmosphericpollution,butthatthesefindingsshouldnotbeusedasalicensetopollute.TheauthorsoftheAmbiostudyhavefoundthat（）

A. forestsgetridofleadpollutionfasterthanexpected
B. leadaccumulationsinforestsaremoredifficulttodealwith
C. leaddepositsarewidelydistributedintheforestsoftheUS
D. theupperlayersofsoilinforestsareeasilypollutedbyleademissions

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Questions21to25arebasedonthefollowingpassage.Leaddeposits,whichaccumulatedinsoilandsnowduringthe1960’sand70’s,wereprimarilytheresultofleadedgasolineemissionsoriginatingintheUnitedStates.InthetwentyyearsthattheCleanAirActhasmandatedunleadedgasuseintheUnitedStates,theleadaccumulationworldwidehasdecreasedsignificantly.AstudypublishedrecentlyinthejournalNatureshowsthatair-borneleadedgasemissionsfromtheUnitedStatesweretheleadingcontributortothehighconcentrationofleadinthesnowinGreenland.ThenewstudyisaresultofthecontinuedresearchledbyDr.CharlesBoutron,anexpertontheimpactofheavymetalsontheenvironmentattheNationalCenterforScientificResearchinFrance.AstudybyDr.Boutronpublishedin1991showedthatleadlevelsinarctic(北极的)snowweredeclining.Inhisnewstudy,Dr.BoutronfoundtheratiosofthedifferentformsofleadintheleadedgasolineusedintheUnitedStatesweredifferentfromtheratiosofEuropean,AsianandCanadiangasolinesandthusenabledscientiststodifferentiate(区分)theleadsources.ThedominantleadratiofoundinGreenlandsnowmatchedthatfoundingasolinefromtheUnitedStates.InastudypublishedinthejournalAmbio,scientistsfoundthatleadlevelsinsoilintheNortheasternUnitedStateshaddecreasedmarkedlysincetheintroductionofunleadedgasoline.Manyscientistshadbelievedthattheleadwouldstayinsoilandsnowforalongerperiod.TheauthorsoftheAmbiostudyexaminedsamplesoftheupperlayersofsoiltakenfromthesamesitesof30forestfloorsinNewEngland,NewYorkandPennsylvaniain1980andin1990.Theforestenvironmentprocessedandredistributedtheleadfasterthanthescientistshadexpected.Scientistssaybothstudiesdemonstratethatcertainpartsoftheecosystem(生态系统)respondrapidlytoreductionsinatmosphericpollution,butthatthesefindingsshouldnotbeusedasalicensetopollute.Itcanbeinferredfromthelastparagraphthatscientists（）

A. arepuzzledbythemysteryofforestpollution
B. feelrelievedbytheuseofunleadedgasoline
C. stillconsiderleadpollutionaproblem
D. lacksufficientmeanstocombatleadpollution

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下列属于冷战时代美国对外战略的是（）

A. 参与和扩展战略
B. 超越遏制战略
C. 国家安全战略
D. 缓和战略
E. 遏制战略

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下表是我国四省（直辖市）的常住人口（其中包括在该地居住的离开原籍半年以上的人口）的普查数据，读后完成下列问题。表中内容反映甲、乙、丙三省（）查看材料

A. 已出现人口负增长
B. 人口流动最大
C. 经济发达
D. 是人口大省

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下表是我国四省（直辖市）的常住人口（其中包括在该地居住的离开原籍半年以上的人口）的普查数据，读后完成下列问题。从第五次人口普查到第六次人口普查的10年间，人口数量增长率最高的是（）

A. 甲省
B. 乙省
C. 丙省
D. 丁市

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A. forestsgetridofleadpollutionfasterthanexpected B. leadaccumulationsinforestsaremoredifficulttodealwith C. leaddepositsarewidelydistributedintheforestsoftheUS D. theupperlayersofsoilinforestsareeasilypollutedbyleademissions

下列属于冷战时代美国对外战略的是（）

下表是我国四省（直辖市）的常住人口（其中包括在该地居住的离开原籍半年以上的人口）的普查数据，读后完成下列问题。表中内容反映甲、乙、丙三省（）查看材料

下表是我国四省（直辖市）的常住人口（其中包括在该地居住的离开原籍半年以上的人口）的普查数据，读后完成下列问题。从第五次人口普查到第六次人口普查的10年间，人口数量增长率最高的是（）

A. forestsgetridofleadpollutionfasterthanexpected
B. leadaccumulationsinforestsaremoredifficulttodealwith
C. leaddepositsarewidelydistributedintheforestsoftheUS
D. theupperlayersofsoilinforestsareeasilypollutedbyleademissions