研磨环主要用来研磨平面。
参考答案:错
I'm sorry I didn't hear what you said. I ___ the picture. [ ]
A. was looking at
B. looked at
C. has looked at
D. am looking at
辩证唯物主义认为,事物发展的规律是( )。
A.思维对事物本质的概括和反映
B.事物内在的、本质的、稳固的联系
C.用来整理感性材料的思维形式
D.事物联系和发展的基本环节