The correct answer is B. Database. The key requirement is that multiple users must access and edit records at the same time. A database is designed for multiple concurrent users and can lock individual records instead of locking an entire file. A flat file or spreadsheet does not handle simultaneous editing as effectively. A fileshare only provides a shared storage location; it does not provide database-level record locking, indexing, querying, or multiuser data management.
Exact Extract/Reference: The CompTIA Tech+ Study Guide states, "If you need to have multiple concurrent users accessing data, you need a database." It also explains that flat files do not work well when several users try to access them at once, while databases generally lock only at the record level so multiple people can actively use the database at one time.