單項(xiàng)選擇題

A portable dry chemical fire extinguisher discharges by（）.

A.gravity when the extinguisher is turned upside down
B.pressure from a small CO₂ cartridge on the extinguisher
C.air pressure from the hand pump attached to the extinguisher
D.pressure from the reaction when water is mixed with the chemical

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單項(xiàng)選擇題

A portable foam (stored-pressure type) fire extinguisher would be most useful in combating a fire in（）.

A.generators
B.oil drums
C.the bridge
D.combustible metals

單項(xiàng)選擇題

A position obtained by applying only your vessel’s coures and speed to a known position is a（）.

A.dead-reckoning position
B.fix B.estimated position
C.probable position
D.running fix