A ball rolls without slipping. The radius of gyration of the ball about an axis passing through its centre of mass is $k$. If radius of the ball be $R$, then the fractio of total energy associated with its rotation will be
(a) $\frac{k^{2}+R^{2}}{R^{2}}$
(b) $\frac{k^{2}}{R^{2}}$
(c) $\frac{k^{2}}{1 \cdot 2+R^{2}}$
(d) $\frac{R^{2}}{k^{2}+R^{2}}$