The correct answer is D) open the circuit breakers on the distribution panel, one at a time, until the lights no longer indicate a ground. This is the correct procedure because it systematically isolates the grounded circuit by eliminating each circuit one by one until the ground indication is removed. This is the most efficient and practical way to locate the specific grounded circuit without having to check resistances or trace the entire circuit path, which could be time-consuming and impractical on a complex electrical system. The other options, while potentially useful in other troubleshooting scenarios, are not the best first step in this case. Checking resistances or continuity may not directly identify the grounded circuit, and visually tracing the circuit path could be difficult, especially if the ground is not readily apparent.