【Manypeoplethinkofthebrainasamystery.Theydon'tknowmuchaboutintelligenceandhowitworks.Whentheydothinkaboutwhatintelligenceis，manypeoplebelievethatapersonisbornsmart，average，ordumb—andstays】

问题描述：

Manypeoplethinkofthebrainasamystery.Theydon'tknowmuchaboutintelligenceandhowitworks.Whentheydothinkaboutwhatintelligenceis，manypeoplebelievethatapersonisbornsmart，average，ordumb—andstaysthatwayinthewholelife.Butnewresearchshowsthatthebrainismorelikeamuscle—itchangesandgetsstrongerwhenyouuseit.Andscientistshavebeenabletoshowjusthowthebraingrowsandgetsstrongerwhenyoulearn.

Everyoneknowsthatwhenyouliftweights，yourmusclesgetbiggerandyougetstronger.Apersonwhocan'tlift20poundswhenhe/shestartsexercisingcangetstrongenoughtolift100poundsafterworkingoutforalongtime.That'sbecausethemusclesbecomelargerandstrongerwithexercise.Andwhenyoustopexercising，themusclesshrinkandyougetweaker.That'swhypeoplesay“Useitorloseit！”

Butmostpeopledon'tknowthatwhentheypracticeandlearnnewthings，partsoftheirbrainchangeandgetlargeralotlikemusclesdowhentheyexercise.Insidethecortex(皮层)ofthebrainarebillionsoftinynervecells，calledneurons.Thenervecellshavebranchesconnectingthemtoothercellsinacomplicatednetwork.Communicationbetweenthesebraincellsiswhatallowsustothinkandsolveproblems.Whenyoulearnnewthings，thesetinyconnectionsinthebrainactuallymultiplyandgetstronger.Themoreyouchallengeyourmindtolearn，themoreyourbraincellsgrow.Then，thingsthatyouoncefoundveryhardorevenimpossibletodo—likespeakingaforeignlanguageordoingalgebra(代数)—seemtobecomeeasyafterlearningthemforaperiodoftime.Theresultisastronger，smarterbrain.

Scientistsstartedthinkingthatthehumanbraincoulddevelopandchangewhentheystudiedanimals'brains.Theyfoundoutthatanimalsthatlivedinachallengingenvironmentweremoreperspicacious—theywerebetteratsolvingproblemsandlearningnewthings.

1.Accordingtothefirstparagraph，________.

A．thefunctionofourbrainislikethatofthemuscle

B．untilnowit'simpossibletoexplainthebrain'smystery

C．manypeoplebelieveone'sintelligenceisnaturallydetermined

D．one'sbraingrowsstrongerastheageincreases

2.Trainingmusclesiscomparedto________.

A．usingthebr