The correct answer is: B. less than the supply voltage.
A synchronous motor is an AC electric motor that rotates at a speed that is synchronized with the frequency of the AC power supply. The induced emf in a synchronous motor is proportional to the speed of rotation. When the motor is working on leading power factor, the rotor is rotating faster than the synchronous speed. This means that the induced emf is less than the supply voltage.
Option A is incorrect because the induced emf cannot be more than the supply voltage. The supply voltage is the maximum voltage that can be applied to the motor. The induced emf can only be equal to the supply voltage if the motor is working on unity power factor.
Option C is incorrect because the induced emf cannot be equal to the supply voltage if the motor is working on leading power factor. The induced emf can only be equal to the supply voltage if the motor is working on unity power factor.
Option D is incorrect because the induced emf is always less than the supply voltage when the motor is working on leading power factor.