Photochemical smog was first observed in .......... .

Acid rain is caused by,or recent reports of acid rain in some industrial cities are due to the effect of atmospheric pollution by:

$DDT$ residues are rapidly passed through the food chain causing biomagnification because $DDT$ is:

What is the intensity of sound in normal conversation?

Which chemical compound caused the death of thousands of people in the Bhopal gas tragedy?

The presence of large amounts of nutrients in water causes excessive growth of planktonic algae,called.........