Assertion: The positively changed nucleus of an atom has a radius of almost `10^(-15)m`.
Reason: In `alpha`-particle scattering experiment the distance of closest apporach for `alpha`-particles is `~~10^(-15)m`.
A. If both assertion and reason are true and the reason is the correct explanation of the assertion
B. If both assertion and reason are true but reason is not the correct explanation of the assertion
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.