London smog is found in

The gas $A$ has very low reactivity and reaches the stratosphere. It is non-toxic and non-flammable but is dissociated by $UV$ radiations in the stratosphere. The intermediates formed initially from the gas $A$ are:

Which free radical is formed when chlorine monoxide free radical reacts with an oxygen atom?

What is Biochemical Oxygen Demand $(BOD)$?

State the name of components of photochemical smog and mention two solutions to control photochemical smog.

Identify the correct statements from the following:
$i$. In the presence of $UV$ light,$CF_2Cl_2(g)$ gives chlorine free radicals which will react with $O_3(g)$ to form $O_2(g)$.
$ii$. Drinking water with $10 \ ppm$ fluoride is better than drinking water with $1 \ ppm$ fluoride.
$iii$. The maximum permissible concentration of lead in drinking water is $50 \ ppb$.