Concept:Ammonia gas is a basic gas with a pungent smell; it reacts with hydrogen chloride to form ammonium chloride fumes.Explanation:Ammonia NH3 dissolves in water to form ammonium hydroxide, NH4OH, which is basic and turns red litmus paper blue.It has a characteristic pungent smell.With hydrogen chloride gas, it forms dense white fumes of ammonium chloride:NH3(g)+HCl(g)→NH4Cl(s)None of the other gases listed shows these properties.Answer:D. NH3