Which of the following describes current that flows periodically in both directions?

The correct choice is Alternating Current, which is characterized by the periodic reversal of direction in the flow of electric charge. In alternating current, the voltage oscillates in a sinusoidal pattern, meaning it changes its polarity at regular intervals, causing the current to flow first in one direction and then in the opposite direction.

This fundamental property makes alternating current suitable for powering homes and businesses, as it can be easily transformed into different voltage levels using transformers. Additionally, the ability to transmit alternating current over long distances efficiently is a significant advantage, as it helps reduce energy losses.

In contrast, direct current flows only in a single direction and maintains a constant voltage level. Pulsating direct current changes its value over time but still has a unidirectional flow, and voltage current is not a standard term used in electrical terminology. These characteristics highlight why alternating current is specifically identified with periodic flow in both directions.