The mass of a planet is $M$ and its radius is $R$. In order for a body of mass $m$ to escape the gravitational attraction of the planet, its kinetic energy at the surface of the planet must be at least

A.     $\frac{{GMm}}{R}$

B.     $\frac{{GMm}}{{{R^2}}}$

C.     $\frac{{GM}}{R}$

D.     $\frac{{GM}}{{{R^2}}}$

A