What type of circuits are AC series circuits that contain at least one resistor and one inductor?

The correct choice is RL AC circuits because this term specifically refers to alternating current circuits that comprise at least one resistor and one inductor. In these circuits, the resistor provides resistance to the flow of current, while the inductor introduces inductance, affecting how the current and voltage behave over time.

In an RL AC circuit, the presence of the inductor causes a phase shift between the voltage and current, which is a key characteristic of this type of circuit. This phase shift results from the inductor opposing changes in current due to its property of inductance, allowing for energy storage in the magnetic field created by the inductor.

Other types of circuits mentioned, such as RLC AC circuits, would include a capacitor in addition to the resistor and inductor, while RC AC circuits would consist of a resistor and a capacitor. DC circuits, on the other hand, involve direct current and do not exhibit the same behaviors associated with inductive and capacitive reactance, which are pivotal in AC circuit analysis and operation.