Assertion : `DeltaG^(@)=-nFE_(cell)^(@)`.
Reason : `E_(cell)^(@)` should be positive for an electrochemical cell.
A. If both assertion and reason are correct and reason is correct explanation for assertion.
B. If both assertion and reason are correct but reason is not correct explanation for assertion.
C. If assertion is correct but reason is incorrect.
D. If assertion and reason both are incorrect.