据不完全统计，从1689年到1839年清朝官方正式记载的涉外司法诉讼约有39起，这些案件多数由中国政府依照本国法律审理，但外国人自审案件也有11起。这说明当时   

A．外国已攫取在华领事裁判权

B．统治者缺乏近代司法主权观念

C．中国的涉外法律较西方先进

D．涉外司法诉讼以贸易纠纷为主

One of the difficulties in building an SQL-like query language for the Web is the absence of a database （） for this huge, heterogeneous repository of information. However, if we are interested in HTML documents only, we can construct a virtual schema from the implicit structure of these files. Thus, at the highest level of （） , every such document is identified by its Uniform Resource Locator (URL), has a （） 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 set of all HTML documents as a relation: Document(url, title, text, type, length, modif)Where all the （） are character strings. In this framework, an individual document is identified with a （） in this relation. Of course, if some optional information is missing from the HTML document, the associate fields will be left blank, but this is not uncommon in any database.

at the highest level of （）

A．protocol

B．control

C．abstraction

D．presentation