牙周膜的细胞成分有（）
A.结缔组织细胞
B.马氏上皮剩余
C.防御细胞
D.神经、血管相关细胞
E.以上都对
参考答案：E
—I don't think this TV set is of good quality. Can you replace it with a new one?
— _______. But I have to talk to my manager first.[ ]
A. Out of the question
B. I'm sorry
C. Not at all
D. Without question
阻碍创新管理的阻力阻碍包括（）。
A.习惯势力的支配
B.固有经验的引导
C.担心失去已有成果和既得利益
D.对未来的不确定性
