The correct option is D Carbon monoxide
When petrol or diesel goes through the complete combustion then it forms carbon dioxide and water molecules.
But when the supply of air/oxygen is poor then incomplete combustion occur. In incomplete combustion water is still produced, but carbon monoxide and un-burnt carbon particles are released instead of carbon dioxide. Carbon monoxide is a poisonous gas which can lead to many diseases.
In general, for incomplete combustion:
Hydrocarbon + oxygen → carbon monoxide + carbon + water.