Two spheres of equal masses but radii r₁ and r₂ are allowed to fall in a liquid of infinite column. The ratio of their terminal velocities are: 

• A

  1

• B

  ${\mathrm{r}}_1 : {\mathrm{r}}_2$

• C

  ${\mathrm{r}}_2 : {\mathrm{r}}_1$

• D

  $\sqrt{{\mathrm{r}}_1}: \sqrt{{\mathrm{r}}_2}$