What is used to remove particulate matter from industrial exhaust?

Exposure to a noise level of $............$ or more for a short period can damage the eardrums,leading to permanent hearing impairment. (in $,dB$)

Which of the following problems in humans is not caused by noise pollution?

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?

Which of the following is a secondary air pollutant?

What are the various components of domestic sewage? Discuss the effects of discharging sewage into a river.