An organization uses a database management system $($DBMS$)$ as a repository for data. The DBMS$,$ in turn, supports a number of end$-$user developed applications which were created using fourth generation programming languages. Some of the applications update the database. Which of the following is the most important control related to the integrity of the data in the database? A$.$ End users have their read$-$only applications approved by the information systems department before accessing the database. B$.$ Concurrency update controls are in place. C$.$ End$-$user applications are developed on personal computers before being implemented on the mainframe. D$.$ A hierarchical database model is adopted so that multiple users can be served at the same time.