Which one of the following is not a common component of photo-chemical smog?

$A$ farmer is using pesticides in his field. He uses the produce from his field as food for fish. He is told that the fish are not fit for human consumption because large amounts of pesticides were found in the fish cells. How is this possible? Explain.

Polar stratospheric clouds were observed over Antarctica some time ago. How might they have formed,and what happens if some of these clouds break down due to heat in the presence of sunlight?

The greenhouse effect is responsible for global warming. Which gases are responsible for the greenhouse effect?

Match List-$I$ with List-$II$

List-$I$ Industry	List-$II$ Waste Generated
$A$. Steel plants	$I$. Gypsum
$B$. Thermal power plants	$II$. Fly ash
$C$. Fertilizer industries	$III$. Slag
$D$. Paper mills	$IV$. Bio-degradable Wastes

Choose the correct answer from the options given below:

Which of the following,when present in excess in drinking water,causes the disease methemoglobinemia?