$A$ metal sphere of radius $R$ and density $\varrho_{1}$ moves with terminal velocity $v_{1}$ through a liquid of density $\sigma$. Another sphere of the same radius but of density $\varrho_{2}$ moves through the same liquid. Its terminal velocity will be:

• A
  $\left[\frac{\varrho_{1}-\sigma}{\varrho_{2}-\sigma}\right] v_{1}$
• B
  $\left[\frac{\varrho_{2}+\sigma}{\varrho_{1}+\sigma}\right] v_{1}$
• C
  $\left[\frac{\varrho_{1}+\varrho_{2}}{\sigma}\right] v_{1}$
• D
  $\left[\frac{\varrho_{2}-\sigma}{\varrho_{1}-\sigma}\right] v_{1}$