Explanation:
B Given,
$\operatorname{Mass}\left(\mathrm{A}_{1}\right)=27$
$\operatorname{Mass}\left(\mathrm{A}_{2}\right)=125$
We know that, radius of nucleus, $\mathrm{R}=\mathrm{R}_{0}(\mathrm{~A})^{1 / 3}$
Where, $\mathrm{R}_{0}=$ constant
$\mathrm{R}=$ radius of nucleus
$\mathrm{R} \propto(\mathrm{A})^{1 / 3}$
$\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}=\left(\frac{\mathrm{A}_{1}}{\mathrm{~A}_{2}}\right)^{1 / 3}$
$\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}=\left(\frac{27}{125}\right)^{1 / 3}$
$\frac{\mathrm{R}_{1}}{\mathrm{R}_{2}}=\frac{3}{5}$
Hence, $\mathrm{R}_{1}: \mathrm{R}_{2}=3: 5$