A rain drop of radius 0.3 mm falling vertically downwards in air has a terminal velocity of 1 m/s. The viscosity of air is 18 x ${10}^{-5}$ poise. The viscous force on the drop is

• A

  101.73 $\times {10}^{-4} \mathrm{dyne}$

• B

  101.73 $\times {10}^{-5} \mathrm{dyne}$

• C

  $16.95\times {10}^{-5} \mathrm{dyne}$

• D

  16.95$\times {10}^{-4} \mathrm{dyne}$