单项选择题
A.3~6m B.6~8m C.6~10m D.8~12m
A.防火阀 B.排烟阀 C.排烟防火阀 D.防火截止阀
A.10t,15~30t B.10t,10~50t C.11t,30~50t D.11t,15~50t