单项选择题
A.a variable displacement axial piston pump
B.a constant displacement axial piston pump
C.a reciprocating piston pump
D.a centrifugal pump
单项选择题 Which of the following hydraulic systems is not one of the three sub-division of the Hydraulic drive system?（）
单项选择题 It is important with all hydraulic systems to ensure that interlocking arrangements provided for pump or motor control levers are （） before the pump driving motor can be started.
单项选择题 Overload protection on hydraulic system is provided by the use of （）.