In S.I. system, the total energy of the free surface of a liquid drop is $2 \pi$ times the surface tension of the liquid. The diameter of the drop is __________ .

• A

  $\sqrt{3} \mathrm{~m}$
• Correct answer
  B

  $\sqrt{2} \mathrm{~m}$
• C

  $\sqrt{5} \mathrm{~m}$
• D

  $\sqrt{7} \mathrm{~m}$

Hence, the correct answer is option: 'B'.