题目内容：
根据以下材料，回答题
FactorstoInfluencetheLifeSpan
Peoplearelivinglongerthanever,butforsomereason,womenarelivinglongerthanmen．AbabyboybornintheUnitedStatesin2003canexpecttolivetobeabout73,butababygirl,about79．Thisisindeedawidegap,andnoonereallyknowswhyitexists．Thegreaterlongevity(长寿)ofwoman,however,hasbeenknownforcenturies．Itwas,forexample,describedintheseventeenthcentury．However,thedifferencewassmallerthen--thegapisgrowing．"
Anumberofreasonshavebeenproposedtoaccountforthedifferences:Thegapisgreatestinindustrializedsocieties,soithasbeensuggestedthatwomenarelesssusceptibletoworkstrainsthatmayraisetheriskofheartdiseaseandalcoholism．Sociologistsalsotellusthatwomenareencouragedtobelessadventurousthanmen(andthismaybewhytheyaremorecarefuldrivers,involvedinfeweraccidents).
Evensmokinghasbeenimplicatedintheagediscrepancy．Itwasoncesuggestedthatworkingwomenaremorelikelytosmokeandasmorewomenenteredtheworkforce,theagegapwouldbegintoclose,becausesmokingisrelatedtoearlierdeaths．Now,however,weseemorewomensmokingandtheystilltendtolivelongeralthoughtheirlungcancerrateisclimbingsharply.
Onepuzzlingaspectoftheproblemisthatwomendonotappeartobeashealthyasmen．Thatis,theyreportfarmoreillness．Butwhenamanreportsanillness,itismorelikelytobeserious.
Someresearchershavesuggestedthatmenmaydieearlierbecausetheirhealthismorestronglyrelatedtotheiremotions．Forexample,mentendtodiesoonerafterlosingaspousethanwomendo．Menevenseemtobemoreweakenedbylossofajob．(Bothofthesearelinkedwithamarkeddecreaseintheeffectivenessoftheimmunesystem.)Amongmen,deathfollowsretirementwithanalarmingpromptness.
Perhapswearesearchingfortheanswerstooclosetothesurfaceoftheproblem．Perhapstheanswersliedeeperinourbiologicalheritage．Afterall,thephenomenonisnotisolatedtohumans.
Femaleshavetheedgeamongvirtuallyallmammalian(哺乳动物的)species,inthattheygenerallylivelonger．Furthermore,inmanyofthesespeciesthedifferencesbeginatthemomentofconception;therearemoremalemiscarriages(流产)．Inhumans,afterbirth,morebabyboysthanbabygirlsdie.
Whatcanwelearnfromthefirsttwoparagraphs? A．Men'slifespanremainsalmostunchanged.
B．Researchershavefoundthecausesoftheagegap.
C．Theagegapwasnoticedonlyrecently.
D．Themoreadvancedasociety,thegreatertheagegap.
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