The surface tension of a liquid is 5 N/m.  If a thin film of the area 0.02 m2 is formed on a loop, then its surface energy will be

• A

  $5\times {10}^2\mathrm{J}$

• B

  $2.5\times {10}^{-2}\mathrm{J}$

• C

  $2\times {10}^{-1}\mathrm{J}$

• D

  $5\times {10}^{-1}\mathrm{J}$