The term 'bio-magnification' refers to the

Which one of the following statements is true?

What is the result of the presence of excessive nutrients in water bodies?

In agriculture,improper drainage of water leads to:
$I-$ The soil becomes waterlogged.
$II -$ The soil surface draws up salts from the water.
$III -$ Salts are deposited as a thin crust on the land surface.
$IV -$ Salts start accumulating around the roots of the plants.
$V -$ The increasing concentration of salts becomes favorable for crop growth.
$VI -$ It is highly beneficial for agriculture.
Which of the above statements are correct?

The Bhopal gas tragedy in $1984$ was caused by the leakage of which gas?

What happens when nitrates and phosphates are added to a lake?