单项选择题
A.交互捻钢丝绳 B.同向捻钢丝绳 C.对称左、右捻钢丝绳 D.左同向捻钢丝绳
A.800 B.900 C.1000 D.1200
A.1m/s B.0.5m/s C.0.3m/s D.0.1m/s