Answer:
Option A
Explanation:
Nitrogen is an inert gas because of the presence of strong bond. That's why although there is 78% N2 in the atmosphere but nitrogen oxide in not formed under ordinary conditions.
But when temperature is high enough i.e, =2000K, it reacts with oxygen to form nitrogen oxide.
$N_{2}+O_{2} $ $\underrightarrow{-2000K} $ 2NO
Thus, Assertion and reason are true and Reason is the correct explanation of the Assertion