The correct answer is D.
A reluctance-start motor is a type of induction motor that uses the reluctance of the rotor to start the motor. The rotor has salient poles, which are projections on the surface of the rotor that create a magnetic field. The stator has a winding that creates a magnetic field. When the stator winding is energized, the magnetic field from the stator interacts with the magnetic field from the rotor, and the rotor starts to turn.
The air-gap between the rotor and stator is uniform in a reluctance-start motor. This is because the rotor is made of a solid piece of metal, and the stator is made of a laminated steel core. The laminated steel core has a uniform air-gap between the rotor and stator.
The other options are all correct.
A. It is similar to reluctance motor. A reluctance-start motor is a type of reluctance motor.
B. It is basically an induction motor and not a synchronous one. A reluctance-start motor is an induction motor.
C. So far as its basic working principle is concerned, it is similar to shaded pole motor. A reluctance-start motor is similar to a shaded pole motor in that it uses the reluctance of the rotor to start the motor. However, a reluctance-start motor is more efficient than a shaded pole motor.