If the surface tension of a liquid is T, the gain in surface energy for an increase in liquid surface by A is

• A

  ${\mathrm{AT}}^{-1}$

• B

  $\mathrm{AT}$

• C

  ${\mathrm{A}}^2\mathrm{T}$

• D

  ${\mathrm{A}}^2{\mathrm{T}}^2$