单项选择题
A.1/5B.1/10C.1/20D.1/50
A.1/2B.1/4C.1/8D.1/10
A.连接环B.计量杠杆C.承重杠杆D.承重脚
A.200mm x 100mmB.300mm x 200mmC.400mm x 300mmD.600mm x 450mm
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