As per Nuclear Physics there is close relationship between mass number and radius of nucleus. If mass number of A is 216 and mass number of B is 27, then the ratio of nuclear radius $(r_A/r_B)$ of the two elements is:

2 : 1

The correct answer is Option (1) → 2 : 1

The radius of a nucleus (r) is,

$r=r_0A^{1/3}$  [$r_0$ = Constant]

$⇒\frac{r_A}{r_B}=\left(\frac{A_1}{A_2}\right)^{1/3}$

$=\left(\frac{216}{27}\right)^{1/3}=\frac{2}{1}$