Given that mass of the earth is $M$ and its radius is $R$. A body is dropped from a height equal to the radius of the earth above the surface of earth. When it reaches the ground its velocity will be
(A) $\frac{G M}{R}$
(B) $\left[\frac{G M}{R}\right]^{1 / 2}$
(C) $\left[\frac{2 G M}{R}\right]^{1 / 2}$
(D) $\left[\frac{2 G M}{R}\right]$