How can photochemical smog be controlled?

Which one of the following substances used in dry cleaning is a better strategy to control environmental pollution?

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 $50 \ ppb$.

Greenhouse gases can be arranged in the 'Global Warming Potential' $(GWP)$ sequence as:

The greenhouse effect is related to

Which of the following is not an air pollutant?