Concept:A distributed database is a single logical database made up of multiple databases stored at different physical locations and connected through a network.
Explanation:Figure 1 shows database systems placed at several distinct sites that are linked together.
Although each site stores its own data and can manage it independently, users can access the whole data as one database.
This arrangement is not a parallel database, because parallel databases typically use multiple processors sharing the same storage.
It is also not an extranet or the internet, which are network concepts rather than database storage models.
Therefore, the diagram best represents a distributed database.
Answer:A. a distributed database
