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單項(xiàng)選擇題

After putting on a self-contained breathing apparatus, you open the air supply and hear a continuous ringing of a bell.What does this mean?（）.

A.The unit is working properly
B.The face mask is not sealed properly
C.The air bottle needs to be refilled
D.The air supply hose has a leak

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單項(xiàng)選擇題

After using a C0₂ portable extinguisher,it should be（）.

A.put back in service if some CO₂ remains
B.hydrostatically tested
C.retagged
D.recharged

單項(xiàng)選擇題

All dunnage planks and mats must be sent to board（）commencement of loading.

A.prior to
B.during
C.in the period of
D.afterwards

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