单项选择题
A.Control panel B.Paralleling panel C.Load panel D.Busbar
（）can be used to prevent hydraulic system overloaded or...
单项选择题（）can be used to prevent hydraulic system overloaded or keep the pressure of oil outlet from pump constant.
A.Overflow valve B.Reducing valve C.Balancing valve D.Reducing valve or balancing valve
The symbol (GB786√1-93) at right side represents （）A.ov...
单项选择题The symbol (GB786√1-93) at right side represents （）
A.overflow valve B.reducing valve C.relief valve D.sequence valve
