Which of the following has the highest moment of inertia when each of them has the same mass and the same radius?

Let $M$ and $R$ be the mass and radius respectively. Moment of inertia of a ring about any of its diameter is

$I_{\text{ring }}=\frac{1}{2}M{R}^2$

Moment of inertia of a disc about any of its diameter is

$I_{\text{disc }}=\frac{1}{4}M{R}^2$

Moment of inertia of a hollow sphere about any of its diameter is

$I_{\text{hollow sphere }}=\frac{2}{3}M{R}^2$

Moment of inertia of a solid sphere about any of its diameter is

$I_{\text{solid sphere }}=\frac{2}{5}M{R}^2$

Thus, $I_{\text{hollow sphere }}$ is largest.