Whichofthefollowingstatementsis

问题：

阅读材料，回答下面的题目。
ANewStrategytoOvercomeBreastCancerPost-menopausal(绝经后)womenwhowalkforanhouradaycancuttheirchanceofbreastcancersignificantly,astudyhassuggested.Thereport,whichfollowed73,000womenfor17years,foundwalkingforatleastsevenhoursaweekloweredtheriskofthedisease.TheAmericanCancerSocietyteamsaidthiswasthefirsttimereducedriskwasspecificallylinkedtowalking.UKexpertssaiditwasmoreevidencethatlifestyleinfluencedcancerrisk.
ArecentpollforthecharityRamblersaquarterofadultswalkfornomorethananhouraweek,butbeingactiveisknowntoreducetheriskofanumberofcancers.Thisstudy,publishedinCancerEpidemiology,Biomarkers&Prevention,followed73.615womenoutof97,785aged50-74whohadbeenrecruitedbytheAmericanCancerSocietybetween1992and1993,soitcouldmonitortheincidenceofcancerinthegroup.
Theywereaskedtocompletequestionnairesontheirhealthandonhowmuchtimetheywereactiveandparticipatinginactivitiessuchaswalking,swimmingandaerobics(有氧运动)andhowmuchtimetheyspentsittingwatchingtelevisionorreading.Theycompletedthesamequestionnairesattwo-yearintervalsbetween1997and2009.Ofthewomen,47%saidwalkingwastheironlyrecreationalactivity.Thosewhowalkedforatleastsevenhoursperweekhada14%lowerriskofbreastcancercomparedtothosewhowalkedthreeorfewerhoursperweek.
Dr.AlpaPatel,aseniorepidemiologistattheAmericanCancerSocietyinAtlanta,Georgia,wholedthestudy,said:"Giventhatmorethan60%ofwomenreportsomedailywalking,promotingwalkingasahealthyleisure-timeactivitycouldbeaneffectivestrategyforincreasingphysicalactivityamongstpost-menopausalwomen.Wewerepleasedtofindthatwithoutanyotherrecreationalactivity,justwalkingonehouradaywasassociatedwithalowerriskofbreastcancerinthesewomen.""Morestrenuous(紧张的)andlongeractivitiesloweredtheriskevenmore."
BaronessDelythMorgan,chiefexecutiveofBreastCancerCampaign,said:"Thisstudyaddsfurtherevidencethatourlifestylechoicescanplayapartininfluencingtheriskofbreastcancerandevensmallchangesincorporateintoournormalday-to-dayactivitycanmakeadifference."
Sheadded:"Weknowthatthebestweapontoovercomingbreastcanceristheabilitytostopitoccurringinthefirstplace.Thechallengenowishowweturnthesefindingsintoactionandidentifyothersustainablelifestylechangesthatwillhelpuspreventbreastcancer."
AllofthefollowingfactorsrelatingtocancerriskwerementionedintheEXCEPT__________.

A.Mostwomentakewalkingastheironlyrecreationalactivity
B.Walkingwastheonlyrecreationalactivityforabouthalfofthewomen
C.Thestudyaimstotrackthehealthconditionsofitssubjects
D.Irregularwalkingincreasedtheriskofbreastcancerinpost-menopausalwomen

参考答案：B

参考解析：

【答案】B
【解析】根据第三段“Ofthewomen，47％saidwalkingwastheironlyrecreationalactivity．ThosewhowalkedforatleastsevenhourSperweekhada14％lowerriskofbreastcancercomparedtothosewhowalkedthreeorfewerhoursperweek…”可知B选项正确，即散步是大约一半的妇女的唯一的休闲活动。