Passage2 Ifthepopulationoftheearthgoesonincreasingatitspresentrate,therewilleventuallynotbeenoughresourceslefttosustainlifeontheplanet.Bythemiddleofthe21stcentury,ifpresenttrendscontinue,wewillhaveusedupalltheoilthatdrivesourcars,forexample.Evenifscientistsdevelopnewwaysoffeedingthehumanrace,thecrowdedconditionsonearthwillmakeitnecessaryforustolookforopenspacesomewhereelse.Butnoneoftheotherplanetsinoursolarsystemarecapableofsupportinglifeatpresent.Onepossiblesolutiontotheproblem,however,hasrecentlybeensuggestedbyanAmericanscientist,ProfessorCarlSagan. Saganbelievesthatbeforetheearth'sresourcesarecompletelyexhausteditwillbepossibletochangetheatmosphereofVenusandsocreateanewworldalmostaslargeasearthitself.ThedifficultyisthatVenusismuchhotterthantheearthandthereisonlyatinyamountofwaterthere. Saganproposesthatalgaeorganisms,whichcanliveinextremelyhotorcoldatmospheresandatthesametimeproduceoxygen,shouldbebredinconditionssimilartothoseonVenus.Assoonasthishasbeendone,thealgaewillbeplacedinsmallrockets.SpaceshipswillthenflytoVenusandfiretherocketsintotheatmosphere.Inafairlyshorttime,thealgaewillbreakdownthecarbondioxideintooxygenandcarbon. Whenthealgaehavedonetheirwork,theatmospherewillbecomecooler,butbeforemancansetfootonVenusitwillbenecessaryfortheoxygentoproducerain.ThesurfaceoftheplanetwillstillbetoohotformentolandonitbuttherainwilleventuallyfallandinafewyearssomethinglikeearthwillbereproducedonVenus. Algaeareplantsthatcan__________.
A.live in very hot temperatures
B.live in very cold temperatures
C.manufacture oxygen
D.all of the above
正确答案是D