Noise is:

What does '$X$' represent in the given figure?

Salinity of the soil is often caused due to

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?

In a coal-based power plant,electrostatic precipitators are installed to control which of the following?

Which of the following is absent in polluted water?