A disc of paper of radius R has a hole of radius r. It is floating on a liquid of surface tension T. The force of surface tension on the disc is

• A

  $T.3\mathrm{\pi R}$

• B

  $T.2\mathrm{\pi }(\mathrm{R}+\mathrm{r})$

• C

  $T.4\mathrm{\pi }(\mathrm{R}+\mathrm{r})$

• D

  $T.2\mathrm{\pi }(\mathrm{R}-\mathrm{r})$