地下防水混凝土的施工缝位置应留在高出底板上表面（）的墙身上。
A.200mm
B.300mm
C.400mm
D.500mm
参考答案：B
矿山安全技术
《煤矿安全规程》规定，地下矿山主要通风机必须装有反风设施，并能在10min内改变巷道中风流方向，当风流方向改变后主要风机的供给风量不应小于正常供风量的______。
A．30% B．40%C．50% D．60%
His heavy drinking and fond of gambling makes him a poor role model.
A. and fact that he gambles B. and that he gamblesC. and he gambles which D. and gambling
