Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason $R$. Assertion A : The nuclear density of nuclides ${ }_5^{10} B ,{ }_3^6 Li ,{ }_{26}^{56} Fe ,{ }_{10}^{20} Ne$ and ${ }_{83}^{209} Bi$ can be arranged as $\rho_{ Bi }^{ N }>\rho_{ Fe }^{ N }>\rho_{ Ne }^{ N }>\rho_{ B }^{ N }>\rho_{ Li }^{ N }$.

Reason $R$ : The radius $R$ of nucleus is related to its mass number $A$ as $R=R_0 A^{1 / 3}$, where $R_0$ is a constant.

In the light of the above statement, choose the correct answer from the options given below :

• A

  Both $A$ and $R$ are true and $R$ is the correct explanation of $A$

• B

  $A$ is false but $R$ is true

• C

  $A$ is true but $R$ is false

• D

  Both $A$ and $R$ are true but $R$ is $NOT$ the correct explanation of $A$