Transfer of hydraulic fluid between hydraulic system A and B is caused by improper operation of system controls or worn （坏的）equipment.液压系统A和B之间的液压油转移是由于系统控制操作不当或设备 磨损造成的。
A.Uncontrolled system or old equipment cause hydraulic fluid flow from hydraulic system A toB B.If you fail to operate the system control properly or the equipment is damaged, the hydraulic fluid will be transferred between hydraulic system A and B C.Flow of hydraulic fluid between hydraulic system A and B result in accidental operation of system controls or damaged equipment.正确答案B
