Where is the ozone layer located?

Name two gases which are considered to be better than $CFCs$ and cause less damage to the ozone layer.

State one important function of ozone layer in the atmosphere. How is it formed there? Which compounds are responsible for the depletion of ozone layer? How do these compounds enter into the atmosphere?

Explain some harmful effects of agricultural practices on the environment.

What is the estimated amount of waste (in kg) generated by each person in an urban area every day?

In a certain study conducted on the occurrence of $DDT$ along food chains in an ecosystem,the concentration of $DDT$ in grass was found to be $0.5\, ppm$ (parts per million),in sheep it was $2\, ppm$,and in man it was $10\, ppm$. Why was the concentration of $DDT$ maximum in the case of man?