单项选择题
A.50mm B.100mm C.150mm D.200mm
A.20mm B.30mm C.40mm D.50mm
A.标准窄轨车辆 B.标准宽轨车辆 C.窄轨车辆 D.宽轨车辆
A.松动脱落 B.绝缘漏电 C.松动漏油 D.松动漏线
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