One solid sphere $A$ and another hollow sphere $B$ are of same mass and same outer radii. Their moment of inertia about their diameters are respectively $\mathrm { I } _ { \mathrm { A } }$ and $\mathrm { I } _ { \mathrm { B } }$ such that\\
(1) $I _ { A } = I _ { B }$\\
(2) $I _ { A } > I _ { B }$\\
(3) $I _ { A } < I _ { B }$\\
(4) $I _ { A } / I _ { B } = d _ { A } / d _ { B }$ Where $d _ { A }$ and $d _ { B }$ are their densities.