The correct answer is A. Reluctance motor.
A reluctance motor is a type of single-phase motor that is suitable for timing and control purposes. It is a synchronous motor, which means that the speed of the rotor is synchronized with the speed of the stator field. This makes it ideal for applications where precise speed control is required, such as in timing devices and servomechanisms.
Reluctance motors are also relatively simple and inexpensive to manufacture, which makes them a good choice for applications where cost is a major factor.
The other options are not suitable for timing and control purposes.
A series motor is a type of DC motor that has the field winding and the armature winding connected in series. This means that the current through both windings is the same. Series motors are known for their high starting torque, but they are also very inefficient.
A repulsion motor is a type of AC motor that has a stator winding and a rotor winding. The stator winding is connected to an AC power source, and the rotor winding is not connected to anything. When the stator winding is energized, it creates a magnetic field. The rotor winding is then attracted to the stator field, and the motor starts to turn. Repulsion motors are not very efficient, and they are not suitable for timing and control purposes.
A universal motor is a type of AC motor that can be operated on either AC or DC power. It has a stator winding and a rotor winding. The stator winding is connected to an AC power source, and the rotor winding is connected to a commutator and brushes. The commutator and brushes allow the rotor winding to be connected to the AC power source in the correct direction, regardless of the polarity of the power source. Universal motors are not very efficient, and they are not suitable for timing and control purposes.