Smoke, fumes, ash, dust, nitric oxide and sulphur dioxide are the main sources of ________.

Q. Smoke, fumes, ash, dust, nitric oxide and sulphur dioxide are the main sources of ________.

1. Primary Pollutants
2. Secondary pollutants
3. Bio-Degradable Pollutants
4. None of the above

Answer: (a) Primary Pollutants.