In a wire carrying Alternating Current, the electrons move "back and forth", first toward one end of the wire, then toward the other end of the wire. (A)
The + / - polarity of AC is constantly reversing. (B)
AC is most commonly used to power devices that plug into a wall outlet, and very very very seldom to power portable devices. (C)
AC is used at voltages anywhere between several hundred-thousand volts for long-distance interstate power transmission, to 3 or 4 volts coming out of a "wall wart" AC adapter in the house. (D) . Voltage of an AC is easily shifted with a transformer, whereas transformers can't be used for DC.
