What is the maximum allowable oxygen content within the ships cargo tanks, inert gas piping and the vapor recovery system?

Correct Answer: Option C — 8%

The maximum allowable oxygen content in an inerted cargo tank is 8% by volume. This concentration is below the level required to support combustion for most hydrocarbon vapors. Maintaining this level is a fundamental requirement for inert gas system operation to ensure the tank atmosphere remains non-flammable.