Depletion of ozone layer is caused by

How can photochemical smog be controlled?

Excess nitrate in drinking water can cause

Consider the following reactions involving some atmospheric pollutants:
$NO + O_3 \rightarrow NO_2 + O_2$
$NO_2 \xrightarrow{h \nu} NO + O$
$O + O_2 \rightarrow O_3$
$4 NO_2 + O_2 + 2 H_2 O \longrightarrow 4 HNO_3$
$3 CH_4 + 2 O_3 \longrightarrow 3 H_2 C = O + 3 H_2 O$
Based on the above,the formation of formaldehyde from methane in the atmosphere will be controlled by:

Which among the following pairs consists only of herbicides?

Chlorine gas reacts with the aromatic ring of lignin to form which of the following substances?