12.ThefunctionofParagraph1isto______________.A.giveanexampleB.showthemainideaofthepassageC.makeanargumentD.introducethetopicofthepassage13.Mostgeneticchangeshappenbecauseof____________.A.people'sbadlivinghabitsB.environmentalpollutionC.people'sconditionatbirthD.heartdiseaseandcancer14.Theunderlinedword"it"inParagraph6refersto________________.A.thecementB.thefootprintC.theharmfulD.thegeneticchange15.Whichofthefollowingstatementsistrue?A.Thefindingshelptofindtreatmentsforgeneticdamagecausedbysmoking.B.Thefindingshavepreventedmorepeoplefromstartingsmoking.C.Thefindingsofferevidencethatadamagedgenecanhealitself.D.Thefindingsarethefruitofmorethanthreeyears'research