Under the National Electric Code, equipment grounding conductors must be sized based on what factors?

The correct choice revolves around the requirements set forth in the National Electric Code (NEC) regarding the sizing of equipment grounding conductors. According to the NEC, the size of equipment grounding conductors is primarily determined by the size of the conductors used in the circuit and the circuit's current rating.

This ensures that the grounding conductors are capable of safely carrying any fault currents that may occur, thereby providing a sufficient path to ground in case of a fault condition. The sizing is specifically related to handling potential overloads safely, allowing the ground system to function properly under fault conditions without creating hazardous situations such as overheating or failure.

Choosing this option reflects an understanding that grounding conductors must be appropriately sized in relation not only to their function but also to the larger system they serve, incorporating both conductor size and current rating effectively into the equation. This is a critical aspect of electrical safety and system reliability as outlined in the NEC.