Regulations require that cargo pumprooms on tank barges (constructed in 1965) carrying grades B or C liquid cargoes have power ventilation systems which can completely change the air in （）.

A.a subsequent temperature rise will cause the cargo to overflow
B.air pockets may cause the cargo to bubble out of the ullage hole
C.the increased viscosity of the product requires higher loading pressure which increases the chances of a spill
D.the tank valve may be stiff and a spill will occur before the valve can be closed

A.as it warms up it becomes heavier than air
B.the way it reacts with sea water
C.the strong odor it produces
D.its low temperature causes frostbite or freezing

A.the introduction of inert gas into a tank with the object of reducing the oxygen content to below 8% by volume
B.the introduction of inert gas into a gas free tank for the purpose of reducing the oxygen content to below 8% by volume
C.the introduction of inert gas into a cargo tank during cargo discharge to replace the volume of discharged cargo
D.All of the above