Which of the following statements is true for direct current (DC)?

Direct current (DC) is characterized by the flow of electric charge in a constant direction. Unlike alternating current (AC), where the flow reverses direction periodically, DC maintains a steady voltage and current, making it ideal for applications like batteries, electronic devices, and more. This unidirectional flow distinguishably defines DC and supports its use in various electronic circuits and power supplies.

In contrast, the other statements relate inaccurately to the properties of DC. For instance, the notion that DC fluctuates over time is incorrect, as this behavior is typical of AC, not DC. Additionally, the statement that DC cannot be used in batteries contradicts a fundamental reality since batteries are a primary source of DC power. Finally, equating DC with AC is misleading, as they represent two distinct types of electrical current with different applications and behaviors.