Which of the following molecules react with haemoglobin of the blood to produce toxic effect?

$A$ 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.

$A$ water sample has $ppm$ level concentration of following anions:
$F^- = 10; \, SO_4^{2-} = 100; \, NO_3^- = 50$
The anion/anions that make/makes the water sample unsuitable for drinking is/are:

Smog is generally produced in the presence of which of the following?

The depletion of ozone in the atmosphere by chlorofluorocarbons [$CCl_2F_2$] is a ...... statement.

Which of the following industries is the best source of increasing $CO$ levels in the atmosphere?