Two nuclei have their mass numbers in the ratio of 1 : 3. The ratio of their nuclear densities would be :

Question

$\begin {array} {1 1} (1)\;1:1 & \quad (2)\;1:3 \\ (3)\;3:1 & \quad (4)\;(3)^{\large\frac{1}{3}}:1 \end {array}$