Therearetwofactorswhichdetermineanindividual'sintelligence．Thefirstisthesortofbrainheisbornwith．Humanbrainsdifferconsiderably,somebeingmorecapablethanothers．Butnomatterhowgoodabrainhehastobeginwith,anindividualwillhavealoworderofintelligenceunlesshehasopportunitiestolearn．Sothesecondfactoriswhathappenstotheindividual--thesortofenvironmentinwhichheisbroughtup．Ifanindividualishandicappedenvironmentally,itislikelythathisbrainwillfailtodevelopandhewillneverattainthelevelofintelligenceofwhichheiscapable． Theimportanceofenvironmentindetermininganindividual'sintelligencecanbe? demonstratedbythecasehistoryoftheidenticaltwins,PeterandMark．Beingidentical,thetwinshadidenticalbrainsatbirth,andtheirgrowthprocesseswerethesame．Whenthetwinswerethreemonthsold,theirparentsdied,andtheywereplacedinseparatefosterhomes．Peterwasraisedbyparentsoflowintelligenceinanisolatedcommunitywithpooreducationalopportunities．Markwasrearedinthehomeofwell-to-doparentswhohadbeentocollege．Hewasreadtoasachild,senttogoodschools,andgiveneveryopportunitytobestimulatedintellectually．Thisenvironmentaldifferencecontinueduntilthetwinswereintheirlateteens,whentheyweregiventeststomeasuretheirintelligence．Mark'sLQ．was125,twenty-fivepointshigherthantheaverageandfullyfortypointshigherthanhisidenticalbrother．Givenequalopportunities,thetwins,havingidenticalbrains,wouldhavetestedatroughlythesamelevel． Accordingtothepassage,theaverageI．Q．is__________．
A.85
B.100
C.110
D.125
正确答案是B