Which is the correct alternate for hydrolysis constant of ${\mathrm{NH}}_4\mathrm{CN}$ ?

• A

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

• B

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

• C

  $\sqrt{\frac{{\mathrm{K}}_{\mathrm{b}}}{\mathrm{c}}}$

• D

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