Which substance is now used in refrigerators instead of $CFC$s?

What is the main source of chlorofluorocarbon $(CFC)$ pollution?

How can domestic waste be used as manure?

$A.$ Ammonium salts produce haze in the atmosphere.
$B.$ Ozone is produced when atmospheric oxygen reacts with chlorine radicals.
$C.$ Polychlorinated biphenyls act as cleansing solvents.
$D.$ 'Blue baby' syndrome occurs due to the presence of excess nitrate ions in water.
Choose the correct answer from the options given below:

Classical smog is a mixture of .....

Identify the air pollutant which in high concentration leads to stiffness of flower buds?