Which of the following is not a greenhouse gas?

The higher concentration of which gas in air can cause stiffness of flower buds?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. Nitrogen oxides in air	$I$. Eutrophication
$B$. Methane in air	$II$. $pH$ of rain water becomes $5.6$
$C$. Carbon dioxide	$III$. Global warming
$D$. Phosphate fertilisers in water	$IV$. Acid rain

Choose the correct answer from the options given below:

What are the reactions involved in the ozone layer depletion in the stratosphere?

Explain in short: Pollution of the troposphere caused by hydrocarbons.

$A$ large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping,but you find an abundance of phytoplankton. Suggest a reason for the fish kill.