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问题 单项选择题

目前各种城域网建设方案的共同点是在结构上采用三层模式，这三层是：核心交换层、业务汇聚层与_______。

A．应用层

B．物理层

C．接入层

D．传输层

答案

参考答案：C

解析：[知识点] 计算机网络的定义与分类
[评析] 目前各种城域网建设方案的共同点是在结构上采用三层模式，这三层是：核心交换层、业务汇聚层与接入层。

单项选择题

BGP is an inter-autonomous system routing protocol; it is designed to be used between multiple autonomous ( ) . BGP assumes that routing within an autonomous system is done by an intra-autonomous system routing protocol.BGP does not make any assumptions about intra-autonomous system （） protocols employed by the various autonomous systems. Specifically， BGP does not require all autonomous systems to run the same intra-autonomous system routing protocol.

BGP is a real inter-autonomous system routing protocol. It imposes no constraints on the underlying Internet topology. The information exchanged via BGP is sufficient to construct a graph of autonomous systems connectivity from which routing loops may be pruned and some routing ( ) decisions at the autonomous system level may be enforced.

The key feature of the protocol is the notion of Path Attributes. This feature provides BGP with flexibility and expandability. Path （） are partitioned into well-known and optional. The provision for optional attributes allows experimentation that may involve a group of BGP （） without affecting the rest of the Internet.   New optional attributes can be added to the protocol in much the same fashion as new options are added to the Telnet protocol， for instance.

Path （） are partitioned into well-known and optional.

A．states

B．searches 

C．attributes   

D．researches
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单项选择题

文艺复兴运动前，欧洲绘画雕塑中的圣母神态安详、神圣，少有人间之情。而在米开朗琪罗的《哀悼基督》中。圣母是一个容貌端庄美丽的母亲，她的美是直观的，但她的悲哀却是深沉的。圣母形象的这种变化反映了（）

A.神性在艺术造型中的体现

B.人体缺陷在艺术创作中的美化

C.人性在艺术造型中的觉醒

D.造型艺术开始从世俗走向神殿
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