A cord is wound round the circumference of wheel of radius r. The axis of the wheel is horizontal and fixed and moment of inertia about it is I. A weight mg is attached to the free end of the cord and falls from rest. After falling through a distance h, the angular velocity of the wheel will be

• A

  $\sqrt{\frac{2\mathrm{gh}}{\mathrm{I}+\mathrm{mr}}}$

• B

  ${\left[\frac{2\mathrm{mgh}}{1+{\mathrm{mr}}^2}\right]}^{\frac{1}{2}}$

• C

  ${\left[\frac{2\mathrm{mgh}}{\mathrm{I}+2\mathrm{m}}\right]}^{\frac{1}{2}}$

• D

  $\sqrt{2\mathrm{gh}}$