What is the minimum size for insulated copper equipment grounding conductors for wet-niche lighting fixtures?

The minimum size for insulated copper equipment grounding conductors for wet-niche lighting fixtures is indeed 12 AWG. This requirement ensures that the grounding conductor is adequately sized to safely carry any fault current and provide effective grounding for the fixtures installed in wet locations, which present a higher risk of electrical hazards.

Using a conductor that is too small may not adequately handle fault conditions, which could lead to overheating and potential failure of the grounding system, posing safety risks to users and maintenance personnel. Additionally, adhering to the 12 AWG specification aligns with the National Electrical Code (NEC) requirements, which aim to maintain safe practices in electrical installations, especially in environments where moisture is a factor.

The other options, while they represent different sizes of conductors, do not meet the minimum standards necessary for such applications, thereby not providing the same level of safety and reliability required for grounding in wet environments.