Correct option is D
Petrol and Diesel (Options 1 and 2) are fossil fuels that produce significant emissions and are not considered clean or green fuels.
CNG (Compressed Natural Gas) (Option 3) is considered a clean fuel because it produces fewer pollutants compared to petrol and diesel.
Bio-Fuel (Option 4) is also considered a green fuel because it is derived from renewable sources and generally produces lower emissions.