Which of the methods listed below is used to provide the rotational torque to cause an AC generator to turn?

Correct Answer: Option C — Starting of the prime mover.

Mechanical prime movers, such as diesel engines or steam turbines, supply the necessary rotational torque to turn the alternator rotor. Per IEEE 45 and 46 CFR Subchapter J, the prime mover must overcome magnetic drag to produce electrical energy.