A.水泥管、塑料管為0.7m,鋼管為0.5m B.水泥管、鋼管為0.5m,塑料管為0.7m C.塑料管、鋼管為0.5m,水泥管為0.7m D.鋼管為0.5m,水泥管為0.6m,塑料管為0.7m
A.10 B.15 C.20 D.25
A.20 B.25 C.30 D.35