What kind of wiring method is specified for insulated copper equipment grounding conductors?

The correct answer refers to the use of a multiple wire system for insulated copper equipment grounding conductors. This method is specified because utilizing multiple wires allows for the increased reliability and effectiveness of grounding systems. Equipment grounding is critical for safety, and a multiple wire system enhances the ability to provide a path for fault current, ensuring prompt operation of overcurrent protection devices.

In contrast to the other methods, a single wire system may not provide adequate fault tolerance, and utilizing only flexible or rigid conduits limits the versatility in installation and may not meet specific code requirements. A multiple wire system allows for better distribution of grounding paths and can accommodate various configurations and installation environments, making it a preferred choice for electrical safety and compliance.