The correct answer is D. All of the above reasons.
The armature of a synchronous machine is located on the stator, while the field winding is located on the rotor. The armature is associated with large power as compared to the field circuits. This is because the armature windings are connected to the power source, while the field windings are connected to a DC source. The field windings only need to provide enough current to create the magnetic field, while the armature windings need to provide enough current to carry the load.
The armature is also located on the stator because it is difficult to provide high voltage insulation on the rotor. The rotor is rotating at high speed, and any insulation would be subject to a lot of wear and tear. The armature is located on the stator, where it is not subject to the same wear and tear.
Finally, the armature is located on the stator to reduce the number of slip rings on the rotor. Slip rings are used to connect the field windings to the DC source. However, slip rings can be a source of problems, such as arcing and sparking. By locating the armature on the stator, the number of slip rings can be reduced, which can improve the reliability of the machine.