钴铬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：B
－Do you mind my opening the window?
－______. Please do it now.
A. Of course not. B. Yes, I do. C. Certainly
引起急性卡他性结膜炎的病因
A．真菌感染B．过敏反应C．细菌感染D．病毒感染E．支原体感染
