A body attains a height equal to the radius of the earth. The velocity of the body with which it was projected is

• A

  $\sqrt{\frac{GM}{R}}$

• B

  $\sqrt{\frac{2GM}{R}}$

• C

  $\sqrt{\frac{1}{4}\frac{GM}{R}}$

• D

  $\sqrt{\frac{GM}{2R}}$