In India,the most commonly used pesticide $BHC$ is

Where was the attempt to treat wastewater by combining artificial and natural processes carried out?

Arrange the following options in ascending order of their $BOD$ value.
$I.$ Sample of highly polluted pond water.
$II.$ Sample from unpolluted pond water.
$III.$ Distilled water.

The Government of India passed the Environment (Protection) Act in the year $............$.

Write critical notes on the following:
$(a)$ Eutrophication
$(b)$ Biomagnification
$(c)$ Groundwater depletion and ways for its replenishment

Identify the correctly matched pair.