Which of the following is not a gaseous air pollutant?

The gaseous air pollutants of primary concern in urban settings include sulfur dioxide, nitrogen dioxide, and carbon monoxide; these are emitted directly into the air from the combustion of fossil fuels.Smoke, a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion, is also a pollutant. Hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.