Assertion `(A)`: Dihydrogen is prepared in the laboratory by the action of conc `H_2SO_4` on granular zinc.
Reason `(R)` : Pure hydrogen can be obtained by the action of water on sodium hydride.
A. If both (A) and (R) are correct and (R) is the correct explanation of (A).
B. If both (A) and (R) are correct but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect, but (R) is correct.