c
$2 \mathrm{NO}+\mathrm{O}_{2} \rightleftharpoons 2 \mathrm{NO}_{2}$
$\mathrm{K}_{1}=\frac{\left[\mathrm{N} \mathrm{O}_{2}\right]^{2}}{[\mathrm{N} \mathrm{O}]^{2}\left[\mathrm{O}_{2}\right]} \ldots$ (ii)
$4 \mathrm{NO}+2 \mathrm{Cl}_{2} \rightleftharpoons 4 \mathrm{NOCl}$
$\mathrm{K}_{2}=\frac{[\mathrm{NOCl}]^{4}}{[\mathrm{NO}]^{4}\left[\mathrm{Cl}_{2}\right]^{2}} \ldots$ (ii)
$\mathrm{NO}_{2}+\frac{1}{2} \mathrm{Cl}_{2} \rightleftharpoons \mathrm{NOCl}+\frac{1}{2} \mathrm{O}_{2}$
$\mathrm{K}_{3}=\frac{[\mathrm{NOCl}]\left[\mathrm{O}_{2}\right]^{1 / 2}}{\left[\mathrm{NO}_{2}\right]\left[\mathrm{Cl}_{2}\right]^{1 / 2}} \ldots$ (iii)
divide $\mathrm{K}_{2}$ by square of $\mathrm{K}_{1}^{2}$ $\frac{[\mathrm{NOCl}]^{4}}{[\mathrm{NO}]^{4}\left[\mathrm{Cl}_{2}\right]^{2}} \times \frac{[\mathrm{NO}]^{4}\left[\mathrm{O}_{2}\right]^{2}}{\left[\mathrm{NO}_{2}\right]^{4}}=\frac{[\mathrm{NOCl}]^{4}\left[\mathrm{O}_{2}\right]^{2}}{\left[\mathrm{NO}_{2}\right]^{4}\left[\mathrm{Cl}_{2}\right]^{2}}$
$\mathrm{K}_{2} \times \frac{1}{\mathrm{K}_{1}^{2}}=\mathrm{K}_{3}^{4} \Rightarrow \frac{\mathrm{K}_{2}}{\mathrm{K}_{1}^{2}}=\mathrm{K}_{3}^{4}$