The correct answer is Nitric acid oxidizes hydrogen gas formed in the reaction.Concept:Chemical properties of metals:The metal reacts with oxygen to form metal oxide.Metal + Oxygen ? Metal oxideThe metal reacts with an acid to form a salt.Metal + Acid ? Salt + Hydrogen gasMetals react with water to form oxides or hydroxides.Metal + water ? Metal oxide/ hydroxideMetals do not react with alkalis.Metal + Alkali ? No reactionExplanation:Metals react with dilute acids to form salt and hydrogen gas. The reaction between zinc metal and dilute HCl can be represented by the following equation:Zn (s) + 2HCl (aq.) ? ZnCl2 (aq.) + H2 (g)But when dilute HCl is replaced by nitric acid i.e., HNO3, different products are formed. The reaction between zinc metal and dilute HNO3 can be represented by the following equation:Zn + 4HNO3 ? Zn(NO3)2 + 2H2O + 2NO2?Hydrogen gas is not evolved when a metal reacts with nitric acid.It is because HNO3 is a strong oxidizing agent.It oxidizes the H2 produced into the water and itself gets reduced to any of the nitrogen oxides (N2O, NO, NO2).