(A) : Antibiotics are produced by bacteria and fungi.
(R) : These drugs are not effective against viruses.
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 but (R) is false.
D. If both (A) and (R) are false.