Which of the following describes a circuit that is directly connected to the main service panel?

A circuit that is directly connected to the main service panel is described as a branch circuit. Branch circuits are the conductors between the final overcurrent device, like a circuit breaker or fuse in the main panel, and the outlets they serve, including lights, appliances, and other devices. They are responsible for delivering electrical power to individual locations within a building.

In contrast, a main circuit typically refers to the larger circuits that distribute power from the main service panel to various circuits or areas of a building. Sub-circuits usually refer to circuits that stem from a main branch circuit but are not directly connected to the main service panel. Feeder circuits are utilized to supply power to a sub-panel or secondary distribution panel from the main panel and can carry power to multiple branch circuits as well. Thus, branch circuits specifically connect to and draw power from the main service panel, making them the correct answer.