A satellite of mass $m$ revolves around the earth of radius $R$ at a height $x$ from its surface. If $g$ is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is

Question

( A ) $\frac{gR^2}{R+x}$
( B ) $\frac{gR}{R+x}$
( C ) $(\frac{gR^2}{R+x})^{^{1/2}}$
( D ) $gx$