whiCh oF thE Following stAtEmEnts is not truE oF thE ExhAust systEm
A．it rEgulAtEs thE spEED oF A CAr.
B．it ChAnnEls out thE wAstE proDuCts oF ComBustion.
C．it rEDuCEs thE noisEs gEnErAtED By thE EnginE.
D．it ClEAns up thE Emissions hArmFul to thE EnvironmEnt.