Which city is the most $SO_2$ polluted?

The Air (Prevention and Control of Pollution) Act came into force in:

Which method is used for the removal of sulphur dioxide and ammonia from the polluted air?

Steps taken by the Government of India to control air pollution include:

For the control of air pollution in Delhi, all buses of Delhi were converted to run on $A$ by the end of $B$ as per the directives of the $C$. Complete the given statement by choosing appropriate options for $A-C$.

Identify the full form of $CNG$.