Which one of the following options contains only primary air pollutants?

Hydrocarbons and nitrogen oxides
Hydrocarbons and ozone
Ozone and peroxyacetyl nitrate
Nitrogen oxides and peroxyacetyl nitrate

Correct answer: Hydrocarbons and nitrogen oxides

Solution

Primary pollutants are those released directly into the atmosphere from sources such as vehicles and industries. Hydrocarbons and nitrogen oxides are directly emitted, whereas ozone and peroxyacetyl nitrate are secondary pollutants formed in the atmosphere.

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