题目内容：
Questionsarebasedonthefollowingpassage. Averyimportantworldproblemistheincreasingnumberofpeoplewhoactuallyinhab-itthisplanet.Thelimitedamountoflandandlandresourceswillsoonbeunabletosupportthehugepopulationifitcontinuestogrowatitspresentrate.
Sowhyisthishugeincreaseinpopulationtakingplace?Itisreallyduetothespreadoftheknowledgeandpracticeofwhatisbecomingknownas"DeathControl".Youhavenodoubtheardoftheterm"BirthControl"."DeathControl"issomethingratherdifferent.Itrecognisestheworkofthedoctorsandscientistswhonowkeepalivepeoplewho,notverylongago,wouldhavediedofavarietyofthenincurablediseases.Throughawidevarietyoftechnologicalinnovationsthatincludefarmingmethodsandthecontrolofdeadlydiseases,wehavefoundwaystoreducetherateatwhichwedie.However,thissuccessistheverycauseofthegreatestthreattomankind.
Ifweexaminetheamountoflandavailableforthisever-increasingpopulation,webe-gintoseetheproblem.Ifeveryoneontheplanethadanequalshareofland,wewouldeachhaveabout50,000squaremetres.Thisfigureseemstobequiteencouraginguntilweexam-inetheamountofusablelandweactuallyhave.Morethanthree-fifthsoftheworld'slandcannotproducefood.
Obviously,withsolittlelandtosupportus,weshouldbetakinggreatcarenottoreduceitfurther.Butwearenot!Instead,weareconsumingits"capital"--itsnonrenewablefos-silfuelsandothermineraldepositsthattookmillionsofyearstoformbutwhicharenowbeingdestroyedindecades.Wearealsodoingthesamewithothervitalresourcesnotusu-allythoughtofasbeingnonrenewablesuchasfertilesoils,groundwaterandthemillionsofotherspeciesthatsharetheearthwithus.
Itisaverycommonbeliefthattheproblemsofthepopulationexplosionarecausedmainlybypoorpeoplelivinginpoorcountrieswhodonotknowenoughtolimittheirreproduction.Thisisnottrue.Theactualnumberofpeopleinanareaisnotasimportantastheeffecttheyhaveonnature.Developingcountriesdohaveaneffectontheirenvironment,butitisthepopulationsofrichercountriesthathaveafargreaterimpactontheearthasawhole.
Accordingtothepassage,whatcontributestothepopulationincrease? A．Humanbeings'ignorance.
B．Thefailureof"BirthControl".
C．Thesuccessof"DeathControl".
D．Technologicalinnovations.
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答案解析：