Identify the full form of $CNG$.

In almost all Indian metropolitan cities like Delhi,the major atmospheric pollutant$(s)$ is/are

What pollutant is primarily removed by a scrubber?

Most hazardous metal pollutant of automobile exhaust is

According to the Central Pollution Control Board $(CPCB)$,which particulate size in diameter (in micrometers) of air pollutants is responsible for the greatest harm to human health?

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?