(C) Assertion (A) is true, but Reason (R) is false.
Assertion is correct — hydrogen gas is not evolved when metals react with nitric acid. However, Reason is false because nitric acid is a strong oxidising agent (not reducing agent), which oxidises the hydrogen produced to water.
The key error in the Reason is the wrong identification of nitric acid as a "reducing agent." Nitric acid is a strong oxidising agent — this is a common factual trap in Assertion-Reason questions. Examiners specifically test whether students can spot this reversal. Always remember: HNO₃ oxidises H₂ to H₂O, hence no hydrogen gas is released when metals react with it (except with very dilute HNO₃ and magnesium/manganese).