行驶泵运行前，（）内须装满液压油，液压油清洁度不低于（）级。
参考答案：壳体 NAS1638 9
The little boy is very fat eating too much food.
A．so
B．so of
C．because
D．because of
高强度螺栓是靠什么来紧固标准节的？
