The correct answer is A. lagging.
A single-phase induction motor is a type of electric motor that uses a rotating magnetic field to induce current in the rotor windings, causing the rotor to turn. The power factor of a single-phase induction motor is usually lagging because the current and voltage waveforms are not in phase. This is due to the inductive nature of the rotor windings.
The lagging power factor of a single-phase induction motor can be improved by using a power factor correction capacitor. A power factor correction capacitor is a capacitor that is connected to the motor in parallel. The capacitor provides a leading current that helps to offset the lagging current of the motor. This improves the power factor of the motor and reduces the amount of reactive power that is drawn from the power grid.
Option B is incorrect because a single-phase induction motor is not always leading. The power factor of a single-phase induction motor is usually lagging, but it can be improved by using a power factor correction capacitor.
Option C is incorrect because the power factor of a single-phase induction motor is usually lagging, not unity.
Option D is incorrect because the power factor of a single-phase induction motor is usually lagging, not unity to 0.8 leading.