If $g$ is the acceleration due to gravity on the earth's surface, the gain in the potential energy of object of mass $m$ raised from the surface of the earth to a height equal to the radius $R$ of the earth is

Question

( A ) $2mgR$
( B ) $\frac{1}{2} mgR$
( C ) $mgR$
( D ) $\frac{1}{4} mgR$