牙种植体最常用的材料是（）。
A.钛
B.陶瓷
C.碳素材料
D.高分子材料
E.树脂材料
参考答案：A
_____ it was finished in time.
A．As the work was difficult
B．Difficult as the work was
C．Difficult as was the work
D．As was the work difficult
《建设工程监理规范》规定，未经( )审查同意而实施的工程变更，项目监理机构不得予以计量。
A．专业监理工程师
B．设计代表
C．总监理工程师
D．业主
