For the reaction $2 \mathrm{HI}(\mathrm{g}) \rightleftharpoons \mathrm{H}_2(\mathrm{~g})+\mathrm{I}_2(\mathrm{~g})$ if the degree of dissociation is $\alpha$ and $K_p$ is the equilibrium constant, then
(a) $\alpha=\frac{\sqrt{2 \mathrm{~K}_{\mathrm{p}}}}{1+\sqrt{2 \mathrm{k}_{\mathrm{p}}}}$
(b) $\alpha=\frac{2 \sqrt{K_p}}{1+2 \sqrt{K_p}}$
(c) $\sqrt{2 \mathrm{~K}_{\mathrm{p}}}=\left(\frac{\alpha}{1-\alpha}\right)$
(d) $2 \sqrt{\mathrm{~K}_{\mathrm{P}}}=\left(\frac{\alpha}{1-\alpha}\right)$