大于18°的下山掘进，每（）米必须做一躲避硐。
A、30
B、40
C、50
D、70
参考答案：B
简述民用建筑平面布置防火检查的方法。
To learn English well, we should find opportunities to hear English ______ as much as we can. [ ]
A. speak
B. speaking
C. spoken
D. to speak
