(A) : ADA deficiency is a genetic disease.
(R) : It is caused by a mutation of ADA gene.
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.
