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英语六级阅读备考练习题及答案.docx

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英语六级阅读备考练习题及答案英语六级阅读备考练习题及答案Thelifestoryofthehumanspeciesgoesbackamillionyears,andthereisnodoubtthatmancameonlyrecentlytothewesternhemisphere.Noneofthethousandsofsitesofaboriginal(土著的')habitationuncoveredinNorthandSouthAmericahasantiquitycomparabletothatofoldWorldsites.Man‘soccupationoftheNewWorldmaydateseveraltensofthousandsofyears,butnoonerationallyarguesthathehasbeenhereeven100,000years.SpeculationastohowmanfoundhiswaytoAmericawaslivelyattheoutset,andtheproposedroutesboxedthecompass.Withoneortwonotableexceptions,however,studentsofAmericananthropologysoonsettledfortheplausibleideathatthefirstimmigrantscamebwayofalandbridgethathadconnectedthenortheastcomerofAsiatothenorthwestcornerofNorthAmericaacrosstheBeringStrait.Marinerswereabletosupplythereassuringinformationthatthestraitisnotonlynarrow–itis56mileswide–butalsoshallow,aloweringofthesealevelthereby100feetorsowouldtransformthestraitintoanisthmus(地峡).WithlittleeelsinthewayofevidencetosustaintheBeringStraitlandbridge,anthropologists(人类学家)embracedtheideathatmanwalkeddryshod(不湿鞋的)fromAsiatoAmerica.Towardtheendofthelastcentury,however,itbecameapparentthattheWesternHemispherewastheNewWorldnotonlyformanbutalsoforahostofanimalsandplants.ZoologistsandbotanistsshowedthatnumeroussubjectsoftheirrespectivekingdomsmusthaveoriginatedinAsiaandspreadtoAmerica.Thesefindingswereneitherastonishingnorwhollyunexpected.Suchspreadofpopulationsisnottobeenvisionedasanexodusormassmigration,eveninthecaseofanimals.Itis,rather,aspillingintonewterritorythataccompaniesincreaseinnumbers,withmovementinthedirectionofleastpopulationpressureandmostfavorableecologicalconditions.Buttheimmensetrafficinplantandanimal‘sformsplacedaheavyburdenontheBeringStraitlandbridgeastheanthropologistsaheadenvisionedit.Whereaspurposefulmencouldmaketheirwayacrossanarrowbridge,theslowdiffusionofplantandanimalswouldrequireanavenueasacontinentandavailableforagesatastretch.1.ThemovementofplantsandanimalsformAsiatoAmericaindicates______.A.thattheycouldnothavetraveledacrosst