(A) : The success of mammals is largely due to their ability to maintain a constant body temperature.
(R) : Plants do not possess mechanism to maintain their internal temperature.
A. If both (A) and (R) are true but (R) is not the correct explanation of (A).
B. If both (A) and (R) are true and (R) is the correct explanation of (A).
C. If (A) is true but (R) is false.
D. If both (A) and (R) are false.
