金合金全冠抛光所用抛光剂是
A．氧化铁
B．氧化铬
C．硼砂
D．浮石
E．石膏
参考答案：A
解析：金合金全冠抛光所用抛光剂是氧化铁。
砂及砂石地基每层下料前，用水准仪测定基层高程，用( )控制分层厚度。
A．水准
B．经纬仪
C．靠尺
D．插钎
Which of the following is not mentioned as the products of 3M Co. in this news report().
A.Optical film.
B.Post-it notes.
C.Scotch tape.
D.Desktops.
