The cooking gas cylinder is filled with .......

Biological magnification refers to

Read the following statements carefully and select the correct ones.
$I.$ $UV$ rays are essential for the production as well as degradation of ozone gas.
$II.$ Ozone present in the ionosphere acts as a shield absorbing $UV$ radiation coming from the sun.
$III.$ One-fourth of the incoming solar radiation is reflected by the atmospheric gases and clouds,and only half of the incoming solar radiation falls on the earth's surface,heating it. Of this,only a small portion is reflected back.

Ruthless exploitation and pollution of the environment has increased the magnitude of waste materials,which has disturbed the operations of all important:

All statements regarding $BOD$ (Biochemical Oxygen Demand) are correct,except:

At the beginning of the $20^{th}$ century,forests covered about $.....P.....$ of the land in India. By the end of the century,this had shrunk to $.....Q.....$.