$CFCl_3$ is responsible for the decomposition of ozone to oxygen. Which of the following reacts with ozone to form oxygen?

Which among the following has the highest concentration of $PAN$?

The maximum prescribed concentration of copper in drinking water is ........ $ppm$.

For your agricultural field or garden,you have developed a compost-producing pit. Discuss the process in the light of bad odour,flies,and recycling of wastes for good produce.

Biochemical oxygen demand $(BOD)$ is a measure of organic materials present in water. $A$ $BOD$ value less than $5 \ ppm$ indicates a water sample to be:

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?