The most common source of A.C voltage is:

Explanation

The correct option, "AC generator (alternator)," refers to a device that converts mechanical energy into alternating current (AC) electrical energy. It achieves this conversion through the principle of electromagnetic induction. In an AC generator, a coil of wire is rotated within a magnetic field, causing an alternating current to be induced in the wire. This alternating current produces an AC voltage output. AC generators, also known as alternators, are commonly used in power plants, automobiles, and various other applications as the primary source of AC electricity. They provide a reliable and efficient means of generating AC voltage for powering electrical systems.