A.四 B.五 C.六 D.七
A.《塔式起重機安全規(guī)程》GB/T5144 B.《塔式起重機》GB/T5031 C.《塔式起重機》GB/T5031及《塔式起重機安全規(guī)程》GB/T5144 D.《起重機設計規(guī)范》GB/T3811
A.2m B.3m C.4m D.5m