(A) in alpha particle scattering number of alpha paritcle undergoing head on collision is small.
(R) small fraction of the number of incident particles rebound back.
A. if both assertion and reason are true and reason is the correct explanation of assertion.
B. if both assertion and reason are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false.
D. if both assertion and reason are false.