Final answer:
Sub-panels should be supplied with four conductors to isolate the grounds and neutrals.
Step-by-step explanation:
In sub-panels, the grounds and neutrals should be isolated by supplying with four conductors. These conductors include the live/hot, neutral, ground, and a separate conductor for grounding and bonding the sub-panel. The main purpose of isolating the grounds and neutrals is to ensure electrical safety and prevent electrical hazards.