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1、2004年5月份托福阅读真题及其答案ReadingQuestion1-10Allmammalsfeedtheiryoung.Belugawhalemothers,forexample,nursetheircalvesforsometwentymonths,untiltheyareabouttogivebirthagainandtheiryoungareabletofindtheirownfood.Thebehavioroffeedingoftheyoungisbuiltintothereprodu
2、ctivesystem.Itisanonelectivepartofparentalcareandthedefiningfeatureofamammal,themostimportantthingthatmammals--whethermarsupials,platypuses,spinyanteaters,orplacentalmammals--haveincommon.Butnotallanimalparents,eventhosethattendtheiroffspringtothepoin
3、tofhatchingorbirth,feedtheiryoung.Mostegg-guardingfishdonot,forthesimplereasonthattheiryoungaresomuchsmallerthantheparentsandeatfoodthatisalsomuchsmallerthanthefoodeatenbyadults.Inreptiles,thecrocodilemotherprotectsheryoungaftertheyhavehatchedandtakes
4、themdowntothewater,wheretheywillfindfood,butshedoesnotactuallyfeedthem.Fewinsectsfeedtheiryoungafterhatching,butsomemakeotherarrangement,provisioningtheircellsandnestswithcaterpillarsandspidersthattheyhaveparalyzedwiththeirvenomandstoredinastateofsusp
5、endedanimationsothattheirlarvaemighthaveasupplyoffreshfoodwhentheyhatch.Foranimalsotherthanmammals,then,feedingisnotintrinsictoparentalcare.Animalsaddittotheirreproductivestrategiestogivethemanedgeintheirlifelongquestfordescendants.Themostvulnerablemo
6、mentinanyanimal'slifeiswhenitfirstfindsitselfcompletelyonitsown,whenitmustforageandfendforitself.Feedingpostponesthatmomentuntilayounganimalhasgrowntosuchasizethatitisbetterabletocope.Youngthatarefedbytheirparentsbecomenutritionallyindependentatamuchg
7、reaterfractionoftheirfulladultsize.Andinthemeantimethoseyoungareshieldedagainstthevagariesoffluctuatingofdifficult-to-findsupplies.Onceaspeciesdoestakethestepoffeedingitsyoung,theyoungbecometotallydependentontheextraeffort.Ifbothparentsareremoved,they
8、ounggenerallydonosurvive.1.Whatdoesthepassagemainlydiscuss?A.Thecarethatvariousanimalsgivetotheiroffspring.B.Thedifficultiesyounganimalsfaceinobtainingfood.C.Themethodsthatmammalsusetonursetheiryoung.D.Theimportanceamongyoungmammalsofbecomingi
