Which of the following is a secondary pollutant ?

Options

A. `SO_(2)`
B. `CO_(2)`
C. `CO`
D. `O_(3)`

Answer

D

Explanation

Ozone `(O_(3))` is secondary pollutant as it is formed by the reaction amongst the primary pollutants . On the other hand , `SO_(2)` is primary polluntant . These pollutants persist in the environment in the form they are passed into it . CO is qualitative pollutant . It is considered as pollutant only when its concentration reaches beyond a threshold value in the environment .
`CO_(2)` is a quantitative as well as a primary pollutant .