Concept:Carbon(IV)oxide (CO2) is used in fire extinguishers because it does not support combustion and is denser than air, which helps smother flames.Explanation:When released, CO2 forms a blanket over the burning material.This blanket cuts off the oxygen supply needed for combustion.CO2 is non-combustible and does not react with most burning substances.It is heavier than air, so it settles on the fire and effectively isolates it from oxygen.Other gases like nitrogen(IV)oxide, carbon(II)oxide, and sulphur(IV)oxide are not used for this purpose.Answer:A. Carbon(IV)oxide