Assertion (A) : Hydrogen gas is not evolved when zinc reacts with nitric acid. Reason (R) : Nitric acid oxidises the hydrogen gas produced to water and itself gets reduced.

In Activity 1.3 of the text, we observe that metals like Zinc ($Zn$) react with dilute sulphuric acid ($H_2SO_4$) to evolve hydrogen gas ($H_2$). However, Nitric acid ($HNO_3$) is a very strong oxidizing agent.

• Assertion (A) is true: When $Zn$ reacts with $HNO_3$, $H_2$ gas is not evolved.
• Reason (R) is true: $HNO_3$ oxidizes the $H_2$ produced into water ($H_2O$) and itself gets reduced to nitrogen oxides like $NO_2$, $NO$, or $N_2O$.

Since the oxidizing nature of the acid explains why the gas is converted to water, Reason (R) is the correct explanation for Assertion (A).