Which of the following best describes the nature of AC current?

The nature of AC (alternating current) is accurately described by its flow in a sine wave pattern. AC current periodically reverses direction, which results in the oscillation of the flow over time. This characteristic of alternating current is represented graphically as a sine wave, highlighting the regular rise and fall of voltage and current levels.

This sine wave pattern is crucial for understanding how AC functions in practical applications, such as in household electricity supply and in many electronic devices. The sine wave shape allows for efficient transmission of power over long distances and is a fundamental aspect of how alternating currents behave compared to direct currents (DC), which flow in one constant direction.

The other options misrepresent the properties of AC. AC does indeed flow through resistors, and it is not limited to a fixed frequency; instead, the frequency can vary depending on the application and country. Therefore, describing AC current as flowing in a sine wave pattern encapsulates its fundamental nature.