(A) : A biotic community comprises several interdependent species.
(R) : A biotic community is always dependent on either plants or animals.
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.