$BOD$ of polluted water is estimated by measuring the amount of . . . . . . .

All of the following are the ill effects of particulate pollutants on human health $EXCEPT$ . . . . . .

Disadvantages of chemical agents are:
$I.$ Chemicals are toxic and harmful to human beings and animals.
$II.$ Chemicals pollute the environment and plants.
$III.$ Weedicides used to remove weeds also pollute the soil.
Choose the correct option.

Air pollutants:
$I.$ Cause injury to all living organisms.
$II.$ Reduce growth and yield of crops and cause premature death of plants.
$III.$ Affect the respiratory system of humans and animals.
Which of the statements given above are correct?

Acid rain:
$(a)$ Causes necrosis
$(b)$ Converts chlorophyll-$a$ into phaeophytin
$(c)$ Responsible for formation of $PAN$

The term 'bio-magnification' refers to the