单项选择题
A.低挂高用 B.不应将绳打结使用，以免绳结受力后剪断 C.不应将挂钩直接挂在不牢固物和直接挂在非金属绳上，防止绳被割断 D.使用安全带应做垂直悬挂，高挂低用较为安全
A.15~30mm B.15~40mm C.25~50mm D.20~45mm
A.800mmB.900mmC.1000mmD.1200mm
A.250mm B.500mm C.750mm D.1000mm
A.200mm B.250mm C.300mm D.400mm
A.5m B.6m C.7m D.8m
A.2m B.3m C.4m D.5m
A.1m B.2m C.3m D.4m
A.800mm B.900mm C.1000mm D.1200mm
A.200mm B.400mm C.600mm D.800mm