In the following given reaction, 'A' is

$$ \stackrel{\bullet}{\mathrm{Cl}}+\mathrm{CH}_{4} \rightarrow \mathrm{A}+\mathrm{B} $$

A and B in the above atmospheric reaction step are :

Major product of the following reaction is

A compound ‘$$\mathrm{A}$$’ on reaction with ‘$$\mathrm{X}$$’ and ‘$$\mathrm{Y}$$’ produces the same major product but different by product '$$a$$' and '$$b^{\prime}$$. Oxidation of '$$a$$' gives a substance produced by ants.

'X' and 'Y' respectively are