根据下列内容，回答196-200题。 Waterproblemsinthefuturewillbecomemoreintenseandmorecomplex.Ourincreasingpopulationwilltremendouslyincreaseurbanwastes,primarilysewage.Ontheotherhand,increas-ingdemandsforwaterwilldecreasesubstantiallytheamountofwateravailablefordilutingwastes. Rapidlyexpandingindustrieswhichinvolvemoreandmorecomplexchemicalprocesseswillpro-ducelargevolumesofliquidwastes,andmanyofthesewillcontainchemicalswhicharepoi-sonous.Tofeedourrapidlyexpandingpopulation,agriculturewillhavetobeintensified.Thiswillinvolveever-increasingquantitiesofagriculturechemicals.Fromthis,itisapparentthatdrasticstepsmustbetakenimmediatelytodevelopcorrectivemeasuresforthepollutionproblem. Therearetwowaysbywhichthispollutionproblemcanbelessened.Thefirstrelatestothetreatmentofwastestodecreasetheirpollutionhazard.Thisinvolvestheprocessingofsolidwastespriortodisposalandthetreatmentofliquidwastes,oreffluents,topermitthereuseofthewaterorbestreducepollutionuponfinaldisposal. Asecondapproachistodevelopaneconomicuseforallorapartofthewastes.Farmmanureisspreadinfieldsasanutrientororganicsupplement.Effluentsfromsewagedisposalplantsareusedinsomeareasbothforirrigationandforthenutrientscontained.Effluentsfromotherprocess-ingplantsmayalsobeusedasasupplementalsourceofwater.Manyindustries,suchasmeatandpoultryprocessingplants,arecurrentlyconvertingformerwasteproductionintomarketablebyproducts.Otherindustrieshavepotentialeconomicusesfortheirwasteproducts. Thepurposeofthispassageis___________.
A.to warn the reader of the dwindling water supply B.to explain industrial uses of water C.to acquaint the reader with water pollution problems D.to demonstrate various measures to solve the pollution problem正确答案C
