$A$ small metal sphere of mass $M$ and density $d_{1}$,when dropped in a jar filled with liquid,moves with terminal velocity after some time. The viscous force acting on the sphere is ($d_{2} =$ density of liquid,$g =$ gravitational acceleration).

• A
  $Mg(1 - \frac{d_{2}}{d_{1}})$
• B
  $Mg(\frac{d_{2}}{d_{1}})$
• C
  $Mg(1 - \frac{d_{1}}{d_{2}})$
• D
  $Mg - (\frac{d_{1}}{d_{2}})$