A solid sphere of density $\eta$ ( > 1) times lighter than water is suspended in a water tank by a string tied to its base as shown in fig. If the mass of the sphere is m then the tension in the string is given by

• A

  $\left(\frac{\mathrm{\eta }-1}{\mathrm{\eta }}\right)\mathrm{mg}$

• B

  $\mathrm{\eta mg}$

• C

  $\frac{\mathrm{mg}}{\mathrm{\eta }-1}$

• D

  $(\mathrm{\eta }-1)\mathrm{mg}$