题目内容：
根据以下材料回答题 Beingamanhasalwaysbeendangerous．Thereareabout105malesbornforevery100fe-males,butthisratiodropstonearbalanceattheageofmaturity,andamong70-year-oldstherearetwiceasmanywomenasmen．Butthegreatuniversalofmalemortalityisbeingchanged．Now,boybabiessurvivealmostaswellasgirlsdo．Thismeansthat,forthefirsttime,therewillbeanexcessofboysinthosecrucialyearswhentheyaresearchingforamate．Moreimportant,anotherchancefornaturalselectionhasbeenremoved．Fiftyyearsago,thechanceofababy(particularlyaboybaby)survivingdependedonitsweight．Akilogramtoolightortooheavymeantalmostcer-taindeath．Todayitmakesalmostnodifference．Sincemuchofthevariationisduetogenes,onemoreagentofevolutionhasgone．
Thereisanotherwaytocommitevolutionarysuicide:stayalive,buthavefewerchildren．
Fewpeopleareasfertileasinthepast．Exceptinsomereligiouscommunities,veryfewwomenhave15children．Nowadaysthenumberofbirths,liketheageofdeath,hasbecomeaverage．
Mostofushaveroughlythesamenumberofoffspring．Again,differencesbetweenpeopleandtheopportunityfornaturalselectiontotakeadvantageofithavediminished．Indiashowswhatishap-pening．Thecountryofferswealthforafewinthegreatcitiesandpovertyfortheremainingtribalpeoples．Thegrandmediocrityoftoday--everyonebeingthesameinsurvivalandnumberofoff-spring--meansthatnaturalselectionhaslost80%ofitspowerinupper-middle-classIndiacom-paredtothetribes．
Forus,thismeansthatevolutionisover;thebiologicalUtopiahasarrived．Strangely,ithasinvolvedlittlephysicalchange．Nootherspeciesfillssomanyplacesinnature．Butinthepast100,000years--eventhepast100years--ourliveshavebeentransformedbutourbodieshavenot．
Wedidnotevolve,becausemachinesandsocietydiditforus．Darwinhadaphrasetodescribethoseignorantofevolution:they"lookatanorganicbeingasasavagelooksataship,asatsome-thingwhollybeyondhiscomprehension"．Nodoubtwewillremembera20thcenturywayoflifebeyondcomprehensionforitsugliness．ButhoweveramazedourdescendantsmaybeathowfarfromUtopiawewere,theywilllookjustlikeus．
Whatusedtobethedangerinbeingamanaccordingtothefirstparagraph? A．Alackofmates．
B．Afiercecompetition．
C．Alowersurvivalrate．
D．Adefectivegene．
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