题目内容：
Questionsarebasedonthefollowingpassage: Animalsseemtohavethesensetoeatwhentheyarehungryandtheydonoteatmorethantheirbodiesneed．Ithasbeendemonstratedthatratswill,whengivenachoiceoveraperiodoftime,preferwaterwithvitaminstowaterwithoutvitaminseventhoughthereisnodifferenceintasteorsmellbetweenthetwowaterbottles．Whenafragrantflavorwasaddedtothevitaminenrichedfluid,theratsdidseemtodevelopatasteforitandkeptdrinkingit,evenafterthevitaminswereswitchedtotheclearwater．Intime,however,theybrokethehabitandwentbacktowherethenecessaryvitaminswere．
Inaclassicexperiment,babiesof6to12monthsoldwereplacedinacafeteriafeedingarrangement,withawideselectionofbabyfoodbeforethem．Theyweregivenwhateverfoodtheypointedtoorappearedinterestedin．Wearetoldthatatfirsttheyshowedsomeunusualeatingpatterns,butthatoveraperiodoftimetheymanagedtoselectwell-balanceddiet．
So,inselectingfood,ratsandbabiesdoseemtoknowandactonwhat'sbestforthem．Apparently,thereisakindof"bodywisdom",whichhmnanssoonlose．Mostofusdonoteataswiselyaswecould．
Manyofourfoodpreferencesareculturallydeterminedandinfluencedbylong-establishedhabits．Somepeopleeatfox,dogandblackbirds,whileweeatcowsandpigs．Sowhatpeopleeatandhowmuchtheyeatseemtobegreatlyinfluencedbywhatisgoingonaroundthem．
Intheexperimentonrats,afragrantflavorwasaddedtotherat'sdrinkingwaterto（ ）． A．encourageratstodrinkvitamin-enrichedwater
B．findoutratspreferenceinflavor
C．testwhetherratsknowwhichdrinkisgoodforthem
D．demonstratethatvitaminsaretasteless
参考答案：
答案解析：