Database: It is a collection of related data organized according to a certain structure and rules. It is a data collection formed by integrating user data. It is a warehouse for storing data. Network: Communication equipment and lines will be in different places and locations A number of relatively independent computers are connected, and certain systems and application software are configured to implement software and hardware resource sharing and information transfer systems between the original independent computers. Network database: based on the background database, plus certain Front-end program, a system that completes data storage, query, and other operations through a browser. According to the above definition, Which of the following systems are not part of the network database (). ['Online video conferencing system of the company headquarters and its subsidiaries.', 'Online banking system capable of realizing online transaction functions.', 'Email systems used by mainstream websites at this stage.', 'Wanfang electronic journal library widely used in universities and research institutes.']