Which of the following is NOT a secondary air pollutant?
A
Aldehydes
B
Nitric oxide
C
Ketones
D
Nitrogen dioxide
Correct Answer: Nitric oxide
Secondary air pollutants are such pollutants whose formation occurs in the atmosphere due to chemical reactions. Nitric oxide is the only given option that is a primary air pollutant. The other options are all examples of secondary pollutants.