$A$ wheel is at rest in a horizontal position. Its moment of inertia about the vertical axis passing through its centre is $I$. $A$ constant torque $\tau$ acts on it for $t$ seconds. The change in rotational kinetic energy is:

• A
  $\frac{\tau^{2} t^{2}}{2 I}$
• B
  $\left[\frac{\tau t}{2 I}\right]$
• C
  $\left[\frac{\tau t}{2 I}\right]^{\frac{1}{2}}$
• D
  $\left[\frac{\tau t}{2 I}\right]^{2}$