What type of current flows in one direction only?

Direct current (DC) flows in one direction only, making it distinct from other types of electrical current. In a DC circuit, the electric charge is constant in polarity, meaning that the electrons flow steadily from the negative terminal to the positive terminal of a power source. This unidirectional flow is utilized in many applications, such as powering batteries, electronic devices, and simple circuits.

Conversely, alternating current (AC) periodically reverses its direction, which is commonly used in household power supply systems. This alternating characteristic of AC makes it suitable for long-distance power transmission but does not fit the criteria of the question. The inclusion of both AC and DC as correct options would imply that both have the same directional flow, which they do not. Thus, direct current is the accurate choice for this question.