阅读文章回答第65~68题CPeoplediettolookmoreattr active.Fishdiettoavoidbeingbeatenup,thrownoutoftheirsocialgroup,andgettingeatenasaresult.Thatisthefascinatingconclusionofthelatestr esearchintofishbehavior.byateamofAustr alianscientists.
Theresearchteamhavediscoveredthatsubordinatefishvoluntarilydiettoavoidchallengingtheirlargercompetitors.“Instudyinggobieswenoticedthatonlythelargesttwoindividuals,amaleandfemale,hadbreeding（繁殖）rightswithinthegroup,”explainsMarianWong.“Allothergroupmembersarenonbreedingfemales,eachbeing5-10%smallerthanitsnextlargestcompetitor.Wewantedtofindouthowtheymaintainthisprecisesizeseparation.”
Thereasonforthesizedifferencewaseasytosee.onceasubordinatefishgrowstowithin5-10%ofthesizeofitslargercompetitor,itcausesafightwhichusuallyendsinthesmallergobybeingdrivenawayfromthegroup.Moreoftenthannot,theevictedfishistheneatenup.
Itappearedthatthesmallerfishwerekeepingthemselvessmallinordertoavoidchallengingthebossfish.Whethertheydidsovoluntarily,byrestr aininghowmuchtheyate,wasnotclear.Theresearchteamdecidedtodoanexperiment.Theytr iedtofattenupsomeofthesubordinategobiestoseewhathappened.Totheirsurprise,thegobiessimplyrefusedtheextr afoodtheywereoffered,clearlypreferringtoremainsmallandavoidfights,overhavingafeast.
Thediscoverychallengesthetr aditionalscientificviewofhowbossindividualskeeptheirpositioninagroup.Previouslyitwasthoughtthatlargeindividualssimplyusedtheirweightandsizetothreatentheirsubordinatesandtakemoreofthefoodforthemselves,sokeepingtheircompetitorssmall.
Whilethehabitsofgobiesmayseemalittlemysterious,Dr.Wongexplainsthatunderstandingtherelationshipsbetweenbossandsubordinateanimalsisimportanttounderstandinghowhierarchical（等级的）societiesremainstable .
Theresearchhasprovedthefactthatvoluntarydietingisahabitfarfromexclusivetohumans.“Asyet,welackacompleteunderstandingofhowwidespreadthevoluntaryreductionoffoodintakeisinnature,”theresearcherscomment.“Dataonhumandietingsuggeststhat,whilehumansgenerallydiettoimprovehealthorincreaseattr activeness,rarelydoesitimprovelong-termhealthandmalesregularlypreferfemalesthatarefatterthanthefemales’ownideal.”
第10题：Whenagobygrowstowithin5-10%ofthesizeofitslargercompetitor,it.
A．facesdanger
B．hasbreedingrights
C．eatsitscompetitor
D．leavesthegroupitself
正确答案：A
