A small ball of mass $$m$$ and density $$\rho$$ is dropped in a viscous liquid of density $$\rho_0$$. After sometime, the ball falls with constant velocity. The viscous force on the ball is :

A

$$mg\left(1 - \rho\rho_0\right)$$

B

$$mg\left(1 + \frac{\rho}{\rho_0}\right)$$

C

$$mg\left(\frac{\rho_0}{\rho} - 1\right)$$

D

$$mg\left(1 - \frac{\rho_0}{\rho}\right)$$