What describes direct current?

Direct current (DC) is characterized by its consistent flow of electric charge in a single direction. This is in contrast to alternating current (AC), which periodically reverses direction. Because DC maintains a steady voltage level, it is commonly used in batteries, electronic devices, and some types of power supplies. The nature of its flow—continuous and unidirectional—enables the reliable operation of various electronic systems and circuits.

In terms of the other descriptions, the option noting that current "flows in alternating directions" describes AC; the "fluctuates regularly" option also pertains to AC, where the flow varies over time in a sinusoidal manner; and the option stating that current "remains static" does not accurately represent DC, as it implies no movement of charged particles at all. In essence, the definition of DC as a flow that is continuous and constant in one direction is what distinctly defines it among types of electrical currents.