始祖鸟在进化上处于哪两类动物的过渡类型．（ ） A．两栖类、鸟类 B．爬行类、鸟

局域网交换机的帧交换需要查询______。

A．端口号/MAC地址映射表

B．端口号/IP地址映射表

C．端口号/介质类型映射表

D．端口号/套接字映射表

表的设计视图分为上下两部分，上半部分是 (7) ，下半部分是 (8) 。

世界上公认的肝炎病毒有五种，在病毒分类学上，属于脱氧核糖核酸(DNA)型的病毒是

A．甲型
B．乙型
C．丙型
D．丁型
E．戊型

世界卫生组织（WHO）在1989年指出，健康应包括生理健康、__________、____________和道德健康。

One of the difficulties in building an SQL-like query lange for the Web is the absence of a database schema for this huge, heterogeneous repository of information. However, if we are interested in HTML documents only, we can construct a virtual (66) from the implicit structure of these files. Thus, at the highest level of (67) , every such document is identified by its Uniform Resource Locator (URL), has a title and a text Also, Web servers provide some additional information such as the type, length, and the last modification date of a document. So, for data mining purposes, we can consider the site of all HTML documents as arelation:
Document (url, (68) , text, type, length, modify)
Where all the (69) are character strings. In this framework, anindividual document is identified with a (70) in this relation. Of course, if some optional information is missing from the HTML document, the associate fields will de left blank, but this is not uncommon in any database.

A．schema

B．relation

C．platform

D．module