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單項(xiàng)選擇題

Class A fires are best extinguished by quenching or cooling with （）.

A.deprival of oxygen
B.a water spray
C.soda-acid
D.foam

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單項(xiàng)選擇題

A fire starts when the following （） factors come together.

A.combustible material
B.ignition source
C.oxygen
D.A and B and C

單項(xiàng)選擇題

（） can be operated independently or locked together and operated as a twin-job cranes of double capacity.

A.Two derricks
B.A derrick and a crane
C.Two cranes
D.A crane and a winch

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