The size of fire hydrant hose connections on a cargo vessel must be either 1-1/2 inches or __________.

Correct Answer: Option B — 2-1/2 inches

46 CFR 76.10-10 specifies that fire hydrant hose connections on cargo vessels must be either 1-1/2 inches or 2-1/2 inches in diameter. This standardization ensures compatibility with shipboard fire hoses and nozzles, allowing for effective firefighting response across different areas of the vessel using standard equipment.