单项选择题
Regulations require that cargo tanks carrying grades D or E liquids on tank barges be vented with（）.
A.gooseneck vents and flame screens
B.pressure-vacuum relief valves
C.branch vent lines and a vent header
D.forced draft blowers
单项选择题 Regulations require that cargo pumps in tankers carrying grade D liquid cargo shall be isolatedfrom sources of vapor ignition by（）.
单项选择题 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 （）.
单项选择题 Petroleum cargo tanks should not be topped off at deck level when loading on a cold day because（）.