单项选择题 Regulations require that tank vessels handling grade B liquids shall have their cargo pumps separated from all sources of vapor ignition by（）.

单项选择题 Regulations require that pumprooms on tank vessels carrying grade C liquid cargo with machinery spaces below the freeboard deck be ventilated with（）.

单项选择题 Regulations require that cargo tanks carrying grades D or E liquids on tank barges be vented with（）.