The correct answer is A. Starter for a car.
A D.C. series motor is invariably tried in a starter for a car because it has a high starting torque. This is because the field current and the armature current are in the same direction, which produces a strong magnetic field. The strong magnetic field causes the armature to rotate quickly, which starts the car.
Option B is incorrect because a D.C. series motor is not a good choice for a drive for a water pump. This is because a D.C. series motor has a high starting torque, but it also has a high speed regulation. This means that the speed of the motor changes a lot with changes in the load. This is not desirable for a water pump, which needs to maintain a constant speed.
Option C is incorrect because a D.C. series motor is not a good choice for a fan motor. This is because a D.C. series motor has a high starting torque, but it also has a high speed regulation. This means that the speed of the motor changes a lot with changes in the load. This is not desirable for a fan motor, which needs to maintain a constant speed.
Option D is incorrect because a D.C. series motor can only operate in D.C.