单项选择题
A.Petroleum and fuel oil
B.Sludge
C.Oil mixed with dredge spoil
D.Oil refuse and oil mixed with wastes
单项选择题 Which step is NOT generally taken when gas-freeing a tank?（）.
单项选择题 Which statement is TRUE concerning the ventilation of engine and fuel tank compartments on uninspected towing vessels using fuel with a flash point of 100°F?（）
单项选择题 Which statement is TRUE concerning protection of double bottom tanks against excessive pressure? （）