The ratio of the relative strengths of strong and weak nuclear forces is

Two protons exert a nuclear force on each other. The distance between them is approximately:

Given below are two statements $:$ one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A) :$ The density of the copper $\left({ }_{29}^{64} Cu \right)$ nucleus is greater than that of the carbon $\left({ }_6^{12} C \right)$ nucleus.
Reason $(R) :$ The nucleus of mass number $A$ has a radius proportional to $A^{1/3}$.
In the light of the above statements,choose the most appropriate answer from the options given below.

Isotopes are atoms having

Which physical quantity is measured in barn?

In the nuclear reaction: $X(n, \alpha) {_3Li^7}$,the term $X$ will be