An excess of ......... $ppm$ of $F^-$ ions in drinking water is responsible for a disease known as fluorosis.

The acceptable level of carbon monoxide gas $(CO)$ in the atmosphere in $ppm$ level is

Which of the following industries is the best source of increasing $CO$ levels in the atmosphere?

What are the adverse effects if industrial and domestic solid waste is not disposed of properly?

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 $50 \ ppb$.

What is the significance of the troposphere for us?