单项选择题
The soda-acid portable extinguishers must be discharged and refilled （）.
A.every six months
B.every year
C.every one and half year
D.every two years
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相关考题
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单项选择题
Class C fires are best extinguished by （）.
A.foam extinguishers
B.water spray equipment
C.dry powder extinguishers
D.soda-acid extinguishers -
单项选择题
Class B fires are best extinguished by smothering, i-e（）.
A.deprival of oxygen
B.removal of heat
C.spraying of water
D.injecting of soda-acid -
单项选择题
Class A fires are best extinguished by quenching or cooling with （）.
A.deprival of oxygen
B.a water spray
C.soda-acid
D.foam
