$A$ wheel of radius $4 \, m$ completes one revolution in $2 \, s$. Find the centripetal acceleration of the wheel.

• A
  ${\pi ^2} \, m/s^2$
• B
  $2{\pi ^2} \, m/s^2$
• C
  $4{\pi ^2} \, m/s^2$
• D
  $8{\pi ^2} \, m/s^2$