单项选择题
A.oil from flowing out of the tank vent
B.air from entering the tank vent
C.vapors from leaving the tank vent
D.flames on deck from entering the tank vent
单项选择题 Functions aboard a tanker or tank barge such as connecting, disconnecting, and topping off must be supervised by（）.
单项选择题 Gasoline tanks should be filled（）.
单项选择题 Generally speaking , the heavier cargo will go into the（）,distributing it evenly fore and aft, the lighter cargo will probably be placed in the（）.