A bucket full of water is rotated in a vertical circle of radius R. If the water does not split out, the speed
of the bucket at topmost point will be

• A

  $\sqrt{Rg}$

• B

  $\sqrt{5gR}$

• C

  $\sqrt{2Rg}$

• D

  $\sqrt{\left(\frac{R}{g}\right)}$