Why are capacitor start motors commonly used?

Capacitor start motors are widely chosen for applications requiring high starting torque, making them particularly suitable for demanding tasks involving heavier loads. The use of a capacitor in the motor circuit enables it to create a phase shift in the current, resulting in a strong magnetic field necessary for initiating operation. This increase in starting torque allows the motor to start and overcome inertia effectively, which is crucial for applications such as compressors, pumps, and other machinery that may need to start under load.

While factors such as cost, size, and electrical input efficiency are important considerations in motor selection, they do not directly contribute to the primary advantage of capacitor start motors, which is their enhanced starting performance. This makes option B the most relevant answer to the question regarding the reason for their common use.