Advantages of D.C Motor over A.C Motor:

1. High Starting Torque:
DC motors have high starting torque which makes them suitable for applications where high torque is required at low speeds. This advantage is not present in AC motors.

2. Wide Speed Range:
DC motors have a wider speed range compared to AC motors. This is because the speed of a DC motor can be easily controlled by changing the armature voltage or the field current. In contrast, the speed of an AC motor is limited by the frequency of the supply voltage.

3. Better Speed Control:
DC motors have excellent speed control characteristics. The speed of a DC motor can be controlled with great precision by varying the armature voltage or the field current. This makes DC motors suitable for applications where precise speed control is required.

4. Low Cost:
DC motors are generally less expensive than AC motors. This is because DC motors have a simpler design and are easier to manufacture.

The answer to the question is option D, "Low Cost", which is not necessarily an advantage of DC motors over AC motors. While it is true that DC motors are generally less expensive than AC motors, this is not always the case. The cost of a motor depends on several factors such as the size, efficiency, and application requirements. In some cases, AC motors may be less expensive than DC motors. Therefore, low cost cannot be considered as a definitive advantage of DC motors over AC motors.