The side of an equilateral triangle is increasing at the rate of $2 \mathrm{~cm} / \mathrm{s}$, then the rate at which the area is increasing when the side of the triangle is $20 \mathrm{~cm}$ is

• A

  $5 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
• B

  $10 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
• C

  $25 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$
• Correct answer
  D

  $20 \sqrt{3} \mathrm{~cm}^2 / \mathrm{s}$

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