单项选择题
A.打密封带B.及时撤离C.封闭现场D.切断电源
A.一不点火 B.二不点火 C.三不点火 D.四不点火
A.5 B.10 C.15 D.20
A.1/2-3/4 B.1/3-1/2 C.1/2-2/3 D.1/3-2/3
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