The correct answer is: A. D.C. shunt motor.
A D.C. shunt motor is a type of electric motor that uses direct current (DC) to power its rotor. The rotor is a rotating part of the motor that is connected to the load. The stator is the stationary part of the motor that contains the windings that produce the magnetic field.
D.C. shunt motors are often used in applications where a constant speed is required, such as in rotary compressors. This is because the speed of a D.C. shunt motor is proportional to the voltage applied to it. This means that if the voltage is kept constant, the speed of the motor will also be constant.
D.C. shunt motors are also relatively easy to control. This is because the speed of the motor can be controlled by adjusting the voltage applied to it. This makes them a good choice for applications where precise speed control is required.
The other options are not as well-suited for driving rotary compressors. A D.C. series motor has a high starting torque, but its speed is not constant. A universal motor can operate on either AC or DC power, but it is not as efficient as a D.C. shunt motor. A synchronous motor has a constant speed, but it requires a special type of power supply.
In conclusion, the correct answer to the question “Which of the following motors one will choose to drive the rotary compressor?” is A. D.C. shunt motor.