单项选择题 You are in charge of a towing vessel that operates exclusively on inland waters. You regularly tow barges that provide services (cargo lighters，fuel barges，etc.) to foreign flag vessels in port. What will be accepted as proper credentials for you and your crew? （）

单项选择题 You are discharging cargo and the inert gas system is in operation to inert the tanks. The pressure in a tank being discharged starts to drop below the allowable limit. What action should you take? （）

单项选择题 You are cleaning the tanks after carrying a cargo of crude oil. Which statement is TRUE? （）