单项选择题
When the tilting box of a variable stroke axial-piston pump is perpendicular to the pump shaft, which of the following conditions will exist?（）
A.The pistons reciprocate B.The ‘B’ end cylinder barrel rotates C.There is no fluid flow D.Power is transmitted hydraulically
单项选择题 The hydraulic oil most likely to thin out when hot and thick when cold would have a viscosity index of（）
单项选择题 When the steering wheel is turned, oil is directed to the steering gear rams by（）
单项选择题 Rudder position is shown on the bridge by the（）
