单项选择题
A cutoff valve in the fire-main system of a ship may be closed to protect the portion of the system on an exposed deck from（）.
A.damage from crane operations B.being used for wash down purposes C.accidental diversion of flow to wrong location D.freezing
单项选择题 A combustible gas indicator meter is calibrated to read the percentage of（）.
单项选择题 A class C fire would be burning（）.
单项选择题 A class B fire is most successfully fought by（）.
