Explanation

(b) When a circuit contains inductance only, then the current lags behind the voltage by the phase difference of $\frac{\pi}{2}\ $or$\ 90{^\circ}$.
While in a purely capacitive circuit, the current leads the voltage by a phase angle of $\ \frac{\pi}{2}\ $or$\ 90{^\circ}$.
In a purely resistive circuit current is in phase with the applied voltage.