题目内容：
根据以下材料，回答题 ActiveinOldAgeKeepsPeopleMobile
Peopleover70whoaren'tactivearemorelikelytodevelopproblemswalkingorclimbingstairswithinafewyears,accordingtoanewstudy.
Thesefindingssuggestthatit'sveryimportanttostay（51）inoldage,studyauthorDr.MarjoleinVissertoldReutersHealth.
"Physicalactivityinoldageisasimportant（52）takingyourmedications(药物),"Vissernoted．"Youdonotneedtojoinanexpensive,fancysportsclubwithhigh-tech(高科技的)equipment．Yourbodywillalready（53）fromregularwalking."
Visser,aDutch(荷兰的)scholar,explainedthat（54）activehelpspreventpeoplefrom
becomingbreathlessduringsimpleactivities,increasemusclemassandstrength,andmaintainthebalancepeopleneedtowalkupstairs,forinstance.
Toinvestigatehowimportantexerciseistoolderadults,Visser'steaminterviewed3,075menand（55）betweentheagesof70and79,allofwhomsaidtheyhadnoproblemswalkingone-quarterofamileorclimbing（56）．Theinvestigatorsfollowedthesubjectsfor4-1/2years,notingwhodevelopedproblems（57）andclimbingstairs.
Duringthestudy,34percentofmenand47（58）ofwomensaidtheybegantostrugglewithwalkingandclimbingstairs．People（59）wereinactiveweretwiceaslikelytoreporttheseproblemsaspeoplewhosaidtheygotregularexercise.
Peoplewhodidn'texercisebuthadactivelifestylesappearedtobeatasomewhathigherriskofdeveloping（60）walkingandclimbingstairs,relativetopeoplewhoexercised（61）Still,leadinganactivelifestyleappearedtoprotectpeople（62）problemsbetterthanbeinggenerallyinactive,theresearchersreportintheJournaloftheAmericanGeriatrics(老年医学)Society.
Amongpeoplewhowereinactive,（63）whowalkedevenalittlebitsuchasbrisk(轻快的)walkingforalittleoveranhourperweek--wereatalower（64）ofmobility(可动性)problems.
"Ifyoudonotliketoexerciseoryoucannotexercise（65）ofserioushealthproblemsorfunctionallimitations,dotrytobeasactiveaspossible,"Visseradvised.
回答(51)题 A．young
B．new
C．still
D．Active
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答案解析：