The correct answer is B) open the circuit breaker in the power supply and tag-out. Before working on any electrical equipment, it is critical to isolate the power supply and prevent accidental energization. Opening the circuit breaker and tagging it out ensures that the equipment cannot be powered on while the work is being performed, which is essential for worker safety. The other options, such as spraying solvents, heating the switch box, or draining condensate, do not directly address the need to isolate the power and may even introduce additional hazards. Proper lock-out/tag-out procedures are a fundamental safety requirement for working on any electrical equipment, as outlined in various regulations and standards, including those specific to the US Coast Guard and maritime operations.