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

Correct Answer: Option D — damage to tank boundaries

Pressure-vacuum (P/V) relief valves are essential safety devices that protect cargo tank structural integrity. They prevent over-pressurization during loading or vacuum collapse during discharge. Maintaining these valves ensures the tank boundaries remain within design limits, preventing catastrophic structural failure or environmental release of hazardous cargo vapors.