根据下列文章，回答21～25题。
Ifyouweretoexaminethebirthcertificatesofeverysoccerplayerin2006'sWorldCuptournamentyouwouldmostlikelyfindanoteworthyquirkelitesoccerlatermonths.IfyouthenexaminedtheEuropeannationalyouthteamsthatfeedtheWorldCupandprofessionalranks，youwouldfindthisstr angephenomenontobeevenmorepronounced.
Whatmightaccountforthisstr angephenomenon？Hereareafewguesses：a）certainastr ologicalsignsconfersuperiorsoccerskills.b）winter-bornbathestendtohavehigheroxygencapacitywhichincreasessoccerstamina.c）soccermadparentsaremorelikelytoconceivechildreninspringtimeattheannualpeakofsoccermania.d）noneoftheabove.
AndersEricsson，a58-year-oldpsychologyprofessoratFloridaStateUniversity，sayshebelievesstr onglyin“noneoftheabove.”EricssongrewupinSweden，andstudiednuclearengineeringuntilherealizedherealizedhewouldhavemoreopportunitytoconducthisownresearchifheswitchedtopsychology.Hisfirstexperimentnearlyyearsago，involvedmemory：tr ainingapersontohearandthenrepeatarandomseriesofnumbers.“Withthefirstsubject.afterabout20hoursoftr aininghisdigitspanhadrisenfrom7to20，”Ericssonrecalls.“Hekeptimproving，andafterabout200hoursoftr aininghehadrisentoover80numbers.”
Thissuccesscoupledwithlaterresearchshowingthatmemoryitselfasnotgeneticallydetermined，ledEricssontoconcludethattheactofmemorizingismoreofacognitiveexercisethananintuitiveone.Inotherwords，whateverinborndifferencestwopeoplemayexhibitintheirabilitiestomemorizethosedifferencesareswampedbyhowwelleachperson“encodes”theinformation.Andthebestwaytolearnhowtoencodeinformationmeaningfully，Ericssondetermined，wasaprocessknownasdeliberatepractice.Deliberatepracticeentailsmorethansimplyrepeatingatask.Rather，itinvolvessettingspecificgoals，obtainingimmediatefeedbackandconcentr atingasmuchontechniqueasonoutcome.Ericssonandhiscolleagueshavethustakentostudyingexpertperformersinawiderangeofpursuits，includingsoccer.Theygatherallthedatatheycan，notjustpredominancestatisticsandbiographicaldetailsbutalsotheresultsoftheirownlavatoryexperimentswithhighachievers.Theirworkmakesaratherstartlingassertion：thetr aitwecommonlycalltalentishighlyoverrated.Or，putanotherway，expertperformerswhetherinmemoryorsurgery，balletorcomputerprogrammingarenearlyalwaysmade，notborn.
第21题Thebirthdayphenomenonfoundamongsoccerplayersismentionedto
A．str esstheimportanceofprofessionaltr aining.
B．spotlightthesoccersuperstarsintheWorldCup.
C．intr oducethetopicofwhatmalesexpertperformance.
D．explainwhysomesoccerteamsplaybetterthanothers.
正确答案：B
