液压油泵必须在发动机怠速下启动；冬季施工时，待油温超过15℃时，方可进入施工工况运转。
参考答案：对
As nobody here knows what is wrong with the machine, we must send for an engineer to ______ the problem.
A．handle
B．raise
C．face
D．present
当前，加工中心进给系统的驱动方式多采用气动伺服进给系统。
