Identify the coldest region among the following layers of atmosphere.

Which of the following is not a greenhouse gas?

$A$ water sample has $ppm$ level concentration of following anions:
$F^- = 10; \, SO_4^{2-} = 100; \, NO_3^- = 50$
The anion/anions that make/makes the water sample unsuitable for drinking is/are:

What are the major pollutants in large cities?

Given below are two statements:
Statement $I$: Chlorofluorocarbons breakdown by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone.
Statement $II$: Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases,which add to the atmosphere.
For the above statements choose the correct answer from the options given below :

What steps should be taken to reduce the production of acid rain?