$A$ saturated solution of $KNO_3$ is used to make a salt bridge because...

• A
  The velocity of $K^{+}$ is greater than that of $NO_3^{-}$.
• B
  The velocity of $NO_3^{-}$ is greater than that of $K^{+}$.
• C
  The velocities of both $K^{+}$ and $NO_3^{-}$ are nearly the same.
• D
  $KNO_3$ is highly soluble in water.