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1、Underthesea李仕才***阅读理解。OldFossilsScientistshavefoundwhattheythinkisprobablytheoldestfossilonEarth,aremnantoflifefrom3.7billionyearsagowhenEarth’sskieswereorangeanditsoceansgreen.InanewlymeltedpartofGreenland,Australianscientistsfoundtheleftoverstructurefromacommunityofmicro
2、bes（微生物）thatlivedonanancientseafloor.Basedontheiranalysisofthefossils,theresearchersdeterminedthattheyare220millionyearsolderthanthosediscoveredinWesternAustralia,whichwere3.48billionyearsold.Thediscoveryshowslifemayhaveformedquickerandmoreeasilythanoncethought,abouthalfab
3、illionyearsafterEarthformed.Andthatmayalsogivehopeforlifeformingelsewhere,suchasMars,saidstudyco-authorMartinVanKranendonkoftheUniversityofNewSouthWalesanddirectoroftheAustralianCenterforAstrobiology.＂Itgivesusanideahowourplanetevolvedandhowlifegainedafoothold,＂VanKranendo
4、nksaid.ScientistshadthoughtitwouldtakeatleasthalfabillionyearsforlifetoformafterthemoltenEarthstartedtocoolabit,butthisshowsitcouldhavehappenedquicker,hesaid.That’sbecausethenewlyfoundfossilisfartoocomplextohavedevelopedsoonaftertheplanet’sfirstlifeforms,hesaid.Inanoutcrop
5、ofrocksthatusedtobecoveredwithiceandsnowwhichmeltedafteranexceptionallywarmspring,theAustralianteamfoundstromatolites（叠层石）,whicharelayeredstructuresthatareoftenproducedbyacommunityofmicrobes.Thestromatoliteswereabout1to4centimetershigh.＂Itislikethehouseleftbehindmadebythem
6、icrobes,＂VanKranendonksaid.＂Scientistsusedthelayersofashfromvolcanoesandtinyzircon（锆石）withuraniumandestimatedthattheydatebackto3.7billionyearsago.＂Thedatingseemsaboutright,saidAbigailAllwood,aNASAastrobiologistwhofoundthepreviousoldestfossil,from3.48billionyearsago,inAustr
7、alia.ButAllwoodsaidshe9isnotcompletelyconvincedthatwhatVanKranendonk’steamfoundoncewasalive.Shesaidtheevidencewasn’tconclusiveenoughthatitwaslifeandnotageologicquirk（地质巧合）.＂Itwouldbenicetohavemoreevidence,butintheserocksthat’salottoask,＂Allwoodsaidinanemail.1.Theunderlined
8、words＂gainedafoothold＂inParagraph3mean______.A.continuedB.changedC.increasedD.Started2.We
