Nitrogen oxide is considered to be a agent.
a. chemical
b. physical

The correct answer is A. Nitrogen Oxide is considered to be a chemical agent.

Explanation:

Nitrogen Oxide is a gas is produced from the chemical reaction between nitrogen and oxygen in the air during combustion, especially at high temperatures. In places with high traffic density, such as in big cities, the amount of nitrogen oxides released into the air as air pollution can increase significantly. NOx gas is formed in all places where there is combustion - for example in engines.

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