If $\mathrm{g}$ is the acceleration due to gravity at the earth's surface and $\mathrm{r}$ is the radius of the earth, the escape velocity for the body to escape out of earth's gravitational field is $\ldots \ldots \ldots$
(A) $\mathrm{gr}$
(B) $\sqrt{(2 \mathrm{gr})}$
(C) $\mathrm{g} / \mathrm{r}$
(D) $\mathrm{r} / \mathrm{g}$