托福阅读理解考前冲刺题及答案.docx

托福阅读理解考前冲刺题及答案2017托福阅读理解考前冲刺题及答案导语：阅读理解是根据文章内容，找出答案的.一种题目，下面是YJBYS小编提供的2017托福阅读理解考前冲刺题，做完记得对答案哦!Generally,inordertobepreservedinthefossilrecord,organismsmustpossesshardbodypartssuchasshellsorbones.Soft,fleshystructuresarequicklydestroyedbypredatorsordecayedbybacteria.Evenhardpartsleftonthesurfaceforacertainlengthoftimewillbedestroyed.Therefore,organismsmustbeburiedrapidlytoescapedestructionbytheelementsandtobeprotectedagainstagentsofweatheringanderosion.Marineorganismsthusarebettercandidatesforfossilizationthanthoselivingonthelandbecausetheoceanistypicallythesiteofsedimentation,whereasthelandislargelythesiteoferosion.Thebedsofancientlakeswerealsoexcellentsitesforrapidburialofskeletalremainsoffreshwaterorganismsandskeletonsofotheranimals,includingthoseofearlyhumans.Ancientswampswereparticularlyplentifulwithprolificgrowthsofvegetation,whichfossilizedinabundance.Manyanimalsbecametrappedinbogsovergrownbyvegetation.Theenvironmentoftheswampskeptbacterialdecaytoaminimum,whichgreatlyaidedinthepreservationofplantsandanimals.Therapidlyaccumulatingsedimentsinfloodplains,deltas,andstreamchannelsburiedfreshwaterorganisms,alongwithotherplantsandanimalsthathappenedtofallintothewater.Onlyasmallfractionofalltheorganismsthathaveeverlivedarepreservedasfossils.Normally,theremainsofaplantoranimalarecompletelydestroyedthroughpredationanddecay.Althoughitseemsthatfossilizationiscommonforsomeorganisms,forothersitisalmostimpossible.Forthemostpart,theremainsoforganismsarerecycledintheearth,whichisfortunatebecauseotherwisesoilandwaterwouldsoonbecomedepletedofessentialnutrients.Also,mostofthefossilsexposedonEarth'ssurfacearedestroyedbyweatheringprocesses.Thismakesforanincompletefossilrecordwithpoorornorepresentationofcertainspecies.Thebestfossilsarethosecomposedofunalteredremains.Generally,itistheinorganichardparts,composedmostlyofcalciumcarbonate,thatformthevastmajorityofunalteredfossils.Calciteandaragonitealsocontributedtoasubstantialnumberoffossilsofcertainorganisms.1.Accordingtothepassa