Explanation:

it produces large quantity of carbon monoxide at lower temperature in and nitrogen oxide at Higher temperature.
Diesel engines can produce black soot (or more specifically diesel particulate matter) from their exhaust. The black smoke consists of carbon compounds that have not burned because of local low temperatures where the fuel is not fully atomised.
The lean-burning nature of diesel engines and the high temperatures and pressures of the combustion process result in significant production of gaseous nitrogen oxides (NOx), an air pollutant that constitutes a unique challenge with regard to their reduction.