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1、Underthesea李仕才***阅读理解。OldFossilsScientistshavefoundwhattheythinkisprobablytheoldestfossilonEarth,aremnantoflifefrom3.7billionyearsagowhenEarth’sskieswereorangeanditsoceansgreen.InanewlymeltedpartofGreenland,Australianscientistsfoundtheleftoverstructurefromacommunityofmicrobes(微生物)thatlivedon
2、anancientseafloor.Basedontheiranalysisofthefossils,theresearchersdeterminedthattheyare220millionyearsolderthanthosediscoveredinWesternAustralia,whichwere3.48billionyearsold.Thediscoveryshowslifemayhaveformedquickerandmoreeasilythanoncethought,abouthalfabillionyearsafterEarthformed.Andthatmay
3、alsogivehopeforlifeformingelsewhere,suchasMars,saidstudyco-authorMartinVanKranendonkoftheUniversityofNewSouthWalesanddirectoroftheAustralianCenterforAstrobiology."Itgivesusanideahowourplanetevolvedandhowlifegainedafoothold,"VanKranendonksaid.Scientistshadthoughtitwouldtakeatleasthalfabillion
4、yearsforlifetoformafterthemoltenEarthstartedtocoolabit,butthisshowsitcouldhavehappenedquicker,hesaid.That’sbecausethenewlyfoundfossilisfartoocomplextohavedevelopedsoonaftertheplanet’sfirstlifeforms,hesaid.Inanoutcropofrocksthatusedtobecoveredwithiceandsnowwhichmeltedafteranexceptionallywarms
5、pring,theAustralianteamfoundstromatolites(叠层石),whicharelayeredstructuresthatareoftenproducedbyacommunityofmicrobes.Thestromatoliteswereabout1to4centimetershigh."Itislikethehouseleftbehindmadebythemicrobes,"VanKranendonksaid."Scientistsusedthelayersofashfromvolcanoesandtinyzircon(锆石)withurani
6、umandestimatedthattheydatebackto3.7billionyearsago."Thedatingseemsaboutright,saidAbigailAllwood,aNASAastrobiologistwhofoundthepreviousoldestfossil,from3.48billionyearsago,inAustralia.ButAllwoodsaidsheisnotcompletelyconvincedthatwhatVanKranendonk’steamfoundoncewasalive.Shesaidtheevidencewasn’
7、tconclusiveenoughthatitwaslifeandnotageologicquirk(地质巧合)."Itwouldbenicetohavemoreevidence,butintheserocksthat’salottoask,"Allwoodsaidinanemail.1.Theunderlinedwords"gainedafoothold"inParagraph3mean______.A.continuedB.changedC.increasedD.Started2.Wec