The correct answer is A. pulsating.
A single-phase induction motor has a rotating magnetic field that is produced by two windings: the main winding and the auxiliary winding. The main winding is connected to the power supply, and the auxiliary winding is connected to a capacitor. The capacitor creates a phase difference between the currents in the two windings, which causes the rotating magnetic field.
When the motor is started, the current in the auxiliary winding is high, which creates a strong rotating magnetic field. This field induces a current in the rotor, which causes the rotor to start rotating. However, the current in the auxiliary winding decreases as the motor speeds up, which weakens the rotating magnetic field. This causes the torque developed by the motor to pulsate.
Option B is incorrect because the torque developed by a single-phase induction motor at starting is not uniform. The torque pulsates as the current in the auxiliary winding decreases.
Option C is incorrect because the torque developed by a single-phase induction motor at starting is not none of the above. The torque is pulsating.
Option D is incorrect because the torque developed by a single-phase induction motor at starting is not nil. The torque is pulsating.