Pressure-vacuum relief valves on tank vessel cargo tanks should be kept in good working order to prevent __________.

Correct Answer: Option C — damage to tank boundaries

Pressure-vacuum (P/V) relief valves are critical safety devices required by 46 CFR to protect cargo tank structural integrity. They prevent over-pressurization during loading or vacuum collapse during discharge, ensuring the tank boundaries remain intact and preventing potential catastrophic failure of the vessel's cargo containment system.