Which of the following is NOT one of the major classes of outdoor pollutants? 

A)  carbon 
B)  sulphur 
C)  smog 
D)  nitrogen

Outdoor Pollutants

Harmful substances present in the outdoor environment, often resulting from industrial activities, vehicle emissions, and natural sources, leading to air, water, and soil pollution.

Major Classes

Principal categories or groups into which items, organisms, or concepts are divided based on shared characteristics or properties.

Carbon

A nonmetallic chemical element with symbol C, atomic number 6, and is the basis of all known life on Earth, playing a critical role in the structure, biochemistry, and climate of our planet.