影响吸附油膜形成的主要因素是什么？
参考答案：
○1润滑油与轴颈和轴瓦的材料○2轴颈和轴瓦表面加工质量○3轴承的工作条件。
乙炔站房内的仪表必须应用( )型仪表。
A．防尘
B．防水
C．防爆
D．数字
I went to visit him, I found, _____, that he wasn't at home. [ ]
A. however
B. but
C. and
D. so
to visit him, I found, _____, that he wasn't at home. [ ]