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1、Unit1Art一、阅读理解。OldFossilsScientistshavefoundwhattheythinkisprobablytheoldestfossilonEarth,aremnantoflifefrom3.7billionyearsagowhenEarth’sskieswereorangeanditsoceansgreen.InanewlymeltedpartofGreenland,Australianscientistsfoundtheleftoverstructurefromamunityofmicrobes(
2、微生物)thatlivedonanancientseafloor.Basedontheiranalysisofthefossils,theresearchersdeterminedthattheyare220millionyearsolderthanthosediscoveredinWesternAustralia,whichwere3.48billionyearsold.Thediscoveryshowslifemayhaveformedquickerandmoreeasilythanoncethought,abouthalf
3、abillionyearsafterEarthformed.Andthatmayalsogivehopeforlifeformingelsewhere,suchasMars,saidstudyco-authorMartinVanKranendonkoftheUniversityofNewSouthWalesanddirectoroftheAustralianCenterforAstrobiology."Itgivesusanideahowourplanetevolvedandhowlifegainedafoothold,"Van
4、Kranendonksaid.ScientistshadthoughtitwouldtakeatleasthalfabillionyearsforlifetoformafterthemoltenEarthstartedtocoolabit,butthisshowsitcouldhavehappenedquicker,hesaid.That’sbecausethenewlyfoundfossilisfartooplextohavedevelopedsoonaftertheplanet’sfirstlifeforms,hesaid.
5、Inanoutcropofrocksthatusedtobecoveredwithiceandsnowwhichmeltedafteranexceptionallywarmspring,theAustralianteamfoundstromatolites(叠层石),whicharelayeredstructuresthatareoftenproducedbyamunityofmicrobes.Thestromatoliteswereabout1to4centimetershigh."Itislikethehouseleftbe
6、hindmadebythemicrobes,"VanKranendonksaid."Scientistsusedthelayersofashfromvolcanoesandtinyzircon(锆石)withuraniumandestimatedthattheydatebackto3.7billionyearsago."Thedatingseemsaboutright,saidAbigailAllwood,aNASAastrobiologistwhofoundthepreviousoldestfossil,from3.48bil
7、lionyearsago,inAustralia.ButAllwoodsaidsheisnotpletelyconvincedthatwhatVanKranendonk’steamfoundoncewasalive.Shesaidtheevidencewasn’tconclusiveenoughthatitwaslifeandnotageologicquirk(地质巧合)."Itwouldbenicetohavemoreevidence,butintheserocksthat’salottoask,"Allwoodsaidina
8、nemail.1.Theunderlinedwords"gainedafoothold"inParagraph3mean______.A.continuedB.changedC.increasedD.Started2.WecanlearnfromParagrap