单项选择题
A.every six months B.every year C.every one and half year D.every two years
Class C fires are best extinguished by （）.A.foam exting...
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
Class B fires are best extinguished by smothering, i-e（...
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
Class A fires are best extinguished by quenching or coo...
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
