Assertion
Nitrogen and oxygen are the main components in the atmosphere but do not react to form oxides of nitrogen
Reason
The reaction between nitrogen and oxygen required high temperature.
A. Both assertion and reason are correct and reason is correct explanation of assertion.
B. Both assertion and reason are correct and reason is not the correct explanation of assertion.
C. Assertion is correct but the reason is correct.
D. Assertion is incorrect but the reason is correct.

Hint: The reaction of nitrogen and oxygen depends upon the temperature. The high temperature is not available in the environment.

Complete answer:
In the environment mainly nitrogen and oxygen are present. The nitrogen is present in 78 percent and oxygen is present in 21 percent. Some other gases are also present in the environment such as hydrogen, carbon dioxide, and some inert gases such as neon.
Nitrogen and oxygen are the main components in the atmosphere but do not react to form oxides of nitrogen because the reaction requires high temperature.
The reaction of nitrogen with oxygen for the formation of nitric oxide is represented as follows:
\[{{\text{N}}_{\text{2}}}\,{\text{ + }}\,{{\text{O}}_{\text{2}}}\,\mathop \to \limits^{{\text{high temp}}{\text{.}}} \,{\text{NO}}\]
The nitrogen with oxygen reacts to form nitric oxide.
The nitric oxide reacts with oxygen to form nitrogen dioxide.
The reaction of formation of nitrogen dioxide is as follows:
\[{\text{NO}}\,{\text{ + }}\,{{\text{O}}_{\text{2}}}\,\mathop \to \limits^{{\text{high temp}}{\text{.}}} \,{\text{N}}{{\text{O}}_2}\]
Nitric oxide and nitrogen dioxide are collectively known as oxides of nitrogen.
Generally, the temperature of the environment is not so high, so the reaction of nitrogen with oxygen can take place. So, even the nitrogen with oxygen is present in a large amount in the environment; the reaction in between them is not feasible.
So, both assertion and reason are correct.
The environmental nitrogen and oxygen react to form nitrogen oxides in the presence of lightning stroke.

Therefore, option (A), both assertion and reason are correct and reason is the correct explanation of assertion, is correct.

Note: The lighting stroke is the natural source of nitrogen oxide. The high temperature is provided in combustion in electric power plants. The temperature of the lightning bolt is 54000 degree Fahrenheit.