Peoplehavesmokedcigarettesforalongtimenow.ThetobaccowhichisusedtomakecigaretteswasfirstgrowninwhatisnowpartoftheUnitedStates.ChristopherColumbus,whodiscoveredAmerica,sawtheIndianssmoking.SoonthedriedleavesweretransportedtoEurope.Inthelate1800s,theTurksmadecigarettespopular. Cigarettesmokecontainsatleasttwoharmfulsubstances,tarandnicotine.Tar,whichformsasthetobaccobums,damagesthelungsandthereforeaffectsbreathing.Nicotine,whichisfoundintheleaves,causesthehearttobeatfasterandincreasesthebreathingrate.Nicotineinlargecankillapersonbystoppingaperson′sbreathingmuscles.Smokersusuallytakeinsmallamountsthatthebodycanquicklybreakdown. Nicotinecanmakenewsmokersfeeldizzy(头晕)orsicktotheirstomachs.Theheartrateforyoungsmokersincreases2to3beatsperminute.Nicotinealsolowersskintemperatureandreducesbloodflowinthelegsandfeet.Itplaysanimportantroleinincreasingsmokers′riskofheartdiseaseandstroke. Smokingcigarettesisdangerous.Cigarettesmokingwasthecauseoflungcancerandseveralotherdeadlydiseases. Tobaccofirstappearedin___________.
A.Asia B.Africa C.Europe D.America正确答案D
