单项选择题
A.3000mmB.2400mmC.2100mmD.3250mm
A.120kPaB.40kPaC.80kPaD.140kPa
A.回油孔不畅或堵塞B.换向气缸和气路泄漏C.换向电磁阀坏D.差速器联接螺栓松旷