单项选择题
A.大车双轮缘,小车单轮缘 B.小车双轮缘,大车单轮缘 C.大、小车都为双轮缘 D.大、小车都为单轮缘
A.0.5mB.1mC.5mD.2m
A.0.5m B.1m C.2m D.0.25m