单项选择题
On a class B fire，which portable fire extinguisher would be the LEAST desirable?（）
A.Carbon dioxide B.Water (stored pressure) C.Dry chemical D.Foam
单项选择题 Oily rags stored in a pile that is open to the atmosphere are a hazard because they may（）.
单项选择题 Normally，potable water systems are connected directly to the（）.
单项选择题 Line throwing apparatus aboard ship must contain（）.
