A.1m B.0.5m C.2m D.1.5m
A.5cm B.10cm C.15cm D.20cm
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