Assertion: The alternating current lags behind the emf by a phase angle of `pi'/'2`, when AC flows through an inductor.
Reason: The inductive reactance increases as the frequency of AC source decreases.
Options:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false and R is also false.