Which of the following intensity of sound becomes a pollutant (in $\text{ dB}$)?

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

Differentiate between wet deposition and dry deposition.

$A$: Biomagnification of $DDT$ can enhance the decline in bird population.
$R$: $DDT$ causes thinning of eggshells and their premature breaking by disturbing calcium metabolism.

If $O_2$ is consumed more by microorganisms in water,what does it indicate?

Spraying of pesticide is an example of