[A]: Isolation is a mechanism which prevents interbreeding among other wise potential mates.
[R]: It is the key factor without which all other factors of evolution will merge into jumble of no significance
A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false