Which one of the following is most soluble?

• A

  $\mathrm{CuS}\left({\mathrm{K}}_{\mathrm{sp}}=8\times {10}^{-37}\right)$

• B

  $\mathrm{MnS}\left({\mathrm{K}}_{\mathrm{sp}}=7\times {10}^{-16}\right)$

• C

  ${\text{Bi}}_2{\mathrm{S}}_3\left({\mathrm{K}}_{\mathrm{sp}}=1\times {10}^{-70}\right)$

• D

  ${\mathrm{Ag}}_2\mathrm{S}\left({\mathrm{K}}_{\mathrm{sp}}=6\times {10}^{-51}\right)$