Which is the most widely used insecticide in the world?

Decibel $(dB)$ is a standard abbreviation used for the quantitative expression of

Acid rain is caused by,or recent reports of acid rain in some industrial cities are due to the effect of atmospheric pollution by:

Name an industry which can cause both air and thermal pollution as well as eutrophication.

The most hazardous metal pollutant used in automobiles is .....

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?