质量为m的滑块从半径为R的半球形碗的边缘滑向碗底，过碗底时的速度大小为v，若滑块

无牙颌的分区是根据（）

A.距离义齿边缘远近程度不同

B.各部分骨质致密程度不同

C.承受牙合力的压力不同

D.全口义齿与各部位接触关系不同

E.粘膜及粘膜下组织结构不同

---Why did Tom become wealthy this year?

---Because he sold _________________ he did last year.

A．four times as many furnitures as

B．four times as furnitures many as

C．four times furniture as much as

D．four times as much furniture as

当电源指示灯亮，而运行指示灯不亮（排除指示灯本身故障原因），说明系统已因某种异常而中止了正常的运行。

儿童是主动发展的个体，是外部世界的（），是自身发展的积极促进者。

社会保障制度