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?

Tall chimneys are recommended for factories.

Which air pollutants are removed by the scrubber technique?

Consider the following statements about a scrubber:
$I.$ It is used to remove gases like sulphur dioxide from industrial exhaust.
$II.$ In a scrubber,the exhaust is passed through a spray of water or lime.
$III.$ Water dissolves gases and lime reacts with sulphur dioxide to form a precipitate of calcium sulphate or calcium sulphide.
Which of the statements given above are correct?

According to an estimate in Delhi,the level of $........$ came down significantly between $1997$ and $2002$.