99色精品-9色在线-99色在线-99色视频 国产欧美日产一区二区三区_亚洲精品亚洲人成在线观看_四虎在线精品永久观看_免费一级a一片久久精

單項(xiàng)選擇題

Increased internal leakage, in addition to poor hydraulic system response,and inadequate lubrication, is the result of ().

A.pump bearings in poor condition
B.excessively worn actuator-piston packing
C.broken directional control valve centering springs
D.low hydraulic oil viscosity

微信掃碼免費(fèi)搜題