第二节 完型填空
阅读下面短文，从短文后所给各题的四个选项(A、B、C和D)中选出能填入相应空白处的最佳选项。
Plugging into Electronic Databases
If you are looking 【B1】 information, library shelves arc a good place 【B2】 . But if you need up-to-the-minute data or have specialized needs, you may 【B3】 a computerized database more useful, 【B4】 expensive, and less time consuming. A database, a file of 【B5】 on one subject or family of subjects, can be 【B6】 and maintained in a computer's memory. The speed of the computer then enables you 【B7】 any item in this file almost instantly.
The three main types of databases are statistics, bibliographies, and full text. Statistical databases store vast 【B8】 of numerical data, such as wage and price indexes, census information, foreign exchange rates, and bond prices, bibliographic databases store references and 【B9】 of articles 【B10】 periodicals and newspapers. Full-text databases offer the complete texts of such materials 【B11】 newspaper, magazine and journal articles.
【B12】 databases exist today, and their numbers are 【B13】 . Many companies have their 【B14】 database, 【B15】 is accessible 【B16】 employees through computer terminals or microcomputers. 【B17】 addition, several hundred commercial data bases are now available 【B18】 the public, 【B19】 literally millions of information readily retrievable. These databases cover specific fields, such as law and financial 【B20】 , or general information, such as sports and weather data.
【B1】
A．at
B．on
C．for
D．in