The ozone layer forms naturally by

What do you mean by green chemistry? How will it help decrease environmental pollution?

Which of the following gases causes depletion in the ozone layer?

The stratosphere extends from sea level up to an altitude of $...$ kilometers.

Some reactions of $NO_2$ relevant to photochemical smog formation are:
$NO_{2(g)} \xrightarrow{hv} NO_{(g)} + X$
$X + O_2 \rightarrow Y$
$NO + Y \rightarrow NO_2 + A$
$O + O_2 + M \rightarrow B + M$
Identify $A, B, X$ and $Y$.

Which one of the following is not a common component of photo-chemical smog?