纤连蛋白属于细胞外基质中的哪一类（）。
A.糖胺聚糖
B.蛋白聚糖
C.胶原
D.弹性蛋白
E.非胶原糖蛋白
参考答案：E
— Why don't you like your job?
— It's always being ____ by my director. [ ]
A. watched
B. watched out
C. watched over
D. looked out
口腔环境最重要的缓冲系统是（）.
A.钠、钾、氯
B.硫氰酸盐
C.重碳酸盐
D.硝酸盐和亚硝酸盐
E.磷酸盐
