单项选择题
A.open and individual tank valves open
B.open and the individual tank valves closed
C.closed and the individual tank valves closed
D.closed and the individual tank valves open
单项选择题 In order to reduce the accumulation of static electricity while loading petroleum products，you should（）.
单项选择题 If you are bunkering and you close off one tank in the line of tanks being filled，the rate of flow to other open tanks on the same line will（）.
单项选择题 How must each storage tank for helicopter fuel on a ship be marked?（）