$A$ particle starting from rest moves in a circle of radius $r$. It attains a velocity of $V_{0} \; m/s$ in the $n^{\text{th}}$ round. Its angular acceleration will be

• A
  $\frac{V_{0}}{n} \; rad/s^{2}$
• B
  $\frac{V_{0}^{2}}{2 \pi n r^{2}} \; rad/s^{2}$
• C
  $\frac{V_{0}^{2}}{4 \pi n r^{2}} \; rad/s^{2}$
• D
  $\frac{V_{0}^{2}}{4 \pi n r} \; rad/s^{2}$