请阅读短文，完成此题。 MoveoverMethuselah.FuturegenerationscouldbelivingwellintotheirsecondcenturyandstilldoingSudoku,iflifeexpectancypredictionsaretrue.Increasingbytwoyearseverydecade,theyshownosignsofflatteningout.Averagelifespanworldwideisalreadydoublewhatitwas200yearsago.Sincethe1980s,expertsthoughttheincreaseinlifeexpectancywouldslowdownandthenstop,butforecastershaverepeatedlybeenprovedwrong. Thereasonbehindthesteadyriseinlifeexpectancyis"thedeclineinthedeathrateoftheelderly",saysProfessorTomKirkwoodfromNewcastleUniversity.Hemaintainsthatourbodiesareevolvingtomaintainandrepairthemselvesbetterandourgenesareinvestinginthisprocesstoputoffthedamagewhichwilleventuallyleadtodeath.Asaresult,thereisnoceilingimposedbythereahtiesoftheageingprocess."Thereisnouse-by-datewhenweage.Ageingisnotafixedbiologicalprocess,"Tomsays. Alargestudyofpeopleaged85andovercarriedoutbyProfessorKirkwooddiscoveredthattherewerearemarkablenumberofpeopleenjoyinggoodhealthandindependenceintheirlate80sandbeyond.Withpeoplereachingoldageinbettershape,itissafetoassumethatthisisallduetobettereatinghabits,livingconditions,educationandmedicine. Therearestillmanypeoplewhosufferfrommajorhealthproblems,butmodemmedicinemeansdoctorsarebetteratmanaginglong-termhealthconditionslikediabetes,highbloodpressureandheartdisease."Wearereachingoldagewithlessaccumulativedamagethanpreviousgenerations.Wearelessdamaged,"saysProfessorKirkwood.Oursofterlivesandtheimprovementsinnutritionandhealthcarehavehadadirectimpactonlongevity. Nearlyone-in-fivepeoplecurrentlyintheUKwilllivetoseetheirlOOthbirthday,theOfficeforNationalStatisticspredictedlastyear.LifeexpectancyatbirthhascontinuedtoincreaseintheUK--from73.4yearsfortheperiod1991to1993to77.85yearsfor2007to2009.AreportinSciencefrom2002whichlookedatlifeexpectancypatternsindifferentcountriessince1840concludedthattherewasnosignofanaturallimittolife. ResearchersJimOeppenandDr.JamesVaupelfoundthatpeopleinthecountrywiththehighestlifeexpectancywouldlivetoanaverageageof100inaboutsixdecades.Buttheystoppedshortofpredictinganythingmore. "Thisisfarfrometernity:modestannualincrementsinlifeexpectancywillneverleadtoimmortality,"theresearcherssaid. Wedonotseemtobeapproachinganythinglikethelimitsoflifeexpectancy,saysProfessorDavidLeonfromtheLondonSchoolofHygieneandTropicalMedicine."Therehasbeennoflatteningoutofthebestofthebest--thegroupswhicheveryoneknowshavegoodlifeexpectancyandlowmortalit_y"hesays. Thesegroups,whichtendtobeinthehighersocialandeconomicgroupsinsociety,canliveforseveralyearslongerthanpeopleinlowersocialgroups,promptingcallsforanendtoinequalitieswithinsocieties. Withinpopulations,genesalsohaveanimportantroletoplayindetermininghowlongwecouldsurvivefor---butenvironmentisstillthemostimportantfactor. Itisnosurprisethathealthy-livingsocietieslikeJapanhavethehighestlifeexpectanciesintheworld.Butitwouldstillbeincredibletothinkthatlifeexpectancycouldgoonrisingforever."Iwouldbettherewillbefurtherincreasesinlifeexpectancyandthenitwillprobablybegintoslow,"saysTom,"butwejustdonTtknow." Basedonrecentstudiesmadebyvariousscholars,whichofthefollowingfactorsplaysafundamentalroleinman'slongevity? 查看材料
A.Genes
B.Eating habits
C.Environment
D.Medical condition
正确答案是A