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單項(xiàng)選擇題

Vapor given off by a flammable liquid will burn when ignited provided（）

A.the vapor and air mixture is too rich
B.it is mixed with certain proportions of air
C.the vapor is too little compared to the air
D.it is of heavy toxicity

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When the ship is under attack by pirates,or terrorists,（）needs to be activated.

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B.SSAS
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