Go through the following statements.

I. The dangers of particulate matter that are very small are not removed by electrostatic precipitators.

II. Smokestacks of thermal power plants, smalters and other industries release particulate and gaseous air pollutants together with harmless gases like N 2 ,O 2 , etc.

III. In the 1990s , Delhi ranked first among the 41 most polluted cities of the world.

IV. Air pollution problems in Delhi became so serious that a Public Interest Litigation (PIL) was filed in the

Supreme Court of India.

Which of the above statements are correct.