Q. Which of the following primarily produces Nitrogen dioxide leading to air pollution?
Answer: Diesel Engine
Notes: Diesel engines emit mainly four types of pollutants: carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM) and nitrogen oxides (NOx). Most of the emitted NOx is formed early in the combustion process, when the piston is still near the top of its stroke. Nitrogen oxides are referred as nitrogen oxide (NO) and nitrogen dioxide (NO2). NO constitutes 85–95 % of NOx.