单项选择题
A.settle near the bottom of the bilge
B.settle near the top of the bilge
C.settle evenly throughout all levels of the bilge by mixing with air
D.disperse to atmosphere
单项选择题 Each ship having an inert gas system must have a portable instruments to measure concentrations of hydrocarbon vapor in inert atmospheres and also to measure（）.
单项选择题 Each inert gas system must be designed to supply the cargo tanks with a gas，or mixture of gasses，that has an oxygen content by volume of（）.
单项选择题 Compared to the amount of concentrated foam liquid used，the amount of low expansion mechanical foam produced is（）.