泵和风机日常维护的重要项目是（）。
A.保证外观整洁
B.电压稳定
C.保证冷却系统完好和润滑油不中断
D.保证联轴器干净，要经常擦拭
参考答案：C
_,I'd like to say how much I have enjoyed staying in your comfortable room. [ ]
A. To conclude
B. To include
C. In the conclusion
D. As conclusion
用螺旋测微器测量某金属丝直径的结果如右图所示．该金属丝的直径是（）mm．
