WebSQL is a SQL-like (26) language for extracting information from the weB. Its capabilities for performing navigation of web (27) make it a useful tool for automating several web-related tasks that require the systematic processing of either ail the links in a (28) , all the pages that can be reached from a given URL through (29) that match a pattern, or a combination of both. WebSQL also provides transparent access to index servers that can be queried via the Common (30) Interface.

A．browsers

B．servers

C．hypertexts

D．clients

我国环境保护实行（），实行国家、省、市、县四级环保主管部门及其所属单位。

A.分级管理体制

B.垂直管理体制

C.双重管理体制

D.多重管理体制