题目内容：
根据下列内容，回答题：DGrown-upsareoftensurprisedbyhowwelltheyremembersomethingtheylearnedaschildrenbuthaveneverpracticedstillswimaswellasevereversince．Amanwhenhegetsbackwhohasnothadachancetogoswimmingforyearscaninthewater．Hecangetonabicycleaftermanyyearsandstillrideaway．Hecanplaycatchandhitaballaswellashisson．Amotherwhohasnotthoughtaboutthewordsforyearscanteachherdaughterthepoemthatbegins"Twinkle,twinkle,littlestar"。rememberthestoryofCinderellaorGoldilocksandtheThreeBears.
Oneexplanationisthelawofoverlearninrf,whichcanbestatedasfollows:Oncewehavelearnedsomething,additionallearningtrials(尝试)increasethelengthoftimewewillrememberit.
Inchildhoodweusuallycontinuetopracticesuchskillsasswimming,bicycleriding,andplayingbaseballlongafterwehavelearnedthem．Wecontinuetolistentoandremindourselvesofwordssuchas"Twinkle,twinkle,littlestar"andchildhoodtalessuchasCinderellaandGoldilocks．Wenotonlylearnbutoverleam
Themultinlicatinntables(乘法口诀表)areanexcentiontotheeeneralrulethatweforgetratherquicklythethingsthatwelearninschool,becausetheyareanotherofthethingsweoverlearninchildhood.
Thelawofoverleamingexplainswhycramming(突击学习)foranexamination．thoughitmayresultinapassinggrade,isnotasatisfactorywaytolearnacollegecourse．Bycramming,astudentmaylearnthesubjectwellenoughtogetbyontheexamination,butheislikelysoontoforgetalmosteverythinghelearned.Alittleoverlearning．ontheotherhand,isreallynecessaryforone'sfuturedevelopment.
WhoisthemainideaofparagraphI? A．Peoplerememberwellwhattheylearnedinchildhoo
B．Childrenhaveabettermemorythangrown-up
C．Poemreadingisagoodwaytolearnword
D．Storiesforchildrenarceasytoremembe
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答案解析：