单项选择题

闸瓦折断、磨耗超限时更换,更换闸瓦时,全车闸瓦型式须一致,闸瓦插销剩余厚度不小于:头部10mm,中部6mm,闸瓦插销距轨面距离不小于()mm;

A.15mm
B.20mm
C.25mm
D.30mm