In hydrolysis of a salt of weak acid and strong base, ${\mathrm{A}}^{-} + {\mathrm{H}}_2\mathrm{O} \rightleftharpoons \mathrm{HA} + {\mathrm{OH}}^{-}$, the hydrolysis constant $\left({\mathrm{K}}_{\mathrm{h}}\right)$ is equal to

• A

  $\frac{{\mathrm{K}}_{\mathrm{w}}}{{\mathrm{K}}_{\mathrm{a}}}$

• B

  $\frac{{\mathrm{K}}_{\mathrm{w}}}{{\mathrm{K}}_{\mathrm{b}}}$

• C

  $\sqrt{\frac{{\mathrm{K}}_{\mathrm{a}}}{\mathrm{C}}}$

• D

  $\frac{{\mathrm{K}}_{\mathrm{w}}}{{\mathrm{K}}_{\mathrm{a}} \times {\mathrm{K}}_{\mathrm{b}}}$