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问题 选择题

《百家姓》在不同朝代有不同的排序。“宋代为：赵钱孙李、周吴郑王……明代为：朱奉天运、富有万方……”这种排列主要体现了 [ ]

A、皇权的独尊    

B、中央集权的强化  

C、等级制度的森严    

D、文化专制的扩展

答案

答案：A

单项选择题

关于氟斑牙，下列哪个说法是错误（）

A.氟主要损害釉质发育期牙胚的造釉细胞

B.饮用水是摄入氟的最大来源

C.深层釉质含氟量是表面釉质的11倍左右

D.又称斑釉牙

E.慢性氟中毒患者可有骨骼增殖性变化
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单项选择题

Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept (12) ,examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (13) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.

14（）

A.syntax

B.semantics

C.language

D.format
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