The motor used for the compressors is

The correct answer is: C. capacitor-start capacitor-run motor

A capacitor-start capacitor-run motor is a type of single-phase induction motor that uses two capacitors to start and run the motor. The starting capacitor is used to create a rotating magnetic field that helps the motor start. The running capacitor is used to improve the power factor of the motor and to reduce noise.

Capacitor-start capacitor-run motors are commonly used in compressors, fans, and other applications where a smooth start is required. They are also used in applications where the motor must be started frequently, such as in refrigerators and freezers.

The other options are incorrect because:

• A d.c. series motor is a type of electric motor that uses direct current (DC) to power it. It has a high starting torque and is used in applications where a high starting torque is required, such as in cranes and hoists.
• A shaded pole motor is a type of single-phase induction motor that uses a shading coil to create a rotating magnetic field. It is a simple and inexpensive motor that is used in applications where a low starting torque is required, such as in fans and blowers.
• A reluctance motor is a type of induction motor that uses the reluctance of the magnetic material to create a rotating magnetic field. It is a more efficient motor than a capacitor-start capacitor-run motor, but it is also more expensive.