The correct answer is: C. Relational DBMS
A relational database management system (RDBMS) is a database management system (DBMS) that stores and manages data in a relational database. A relational database is a collection of data items organized as a set of formally described tables from which data can be accessed or reassembled in many different ways without having to reorganize the database tables.
A flat file system is a data storage system that stores data in a single file. The data is not organized in any particular way, and it can be difficult to access and manipulate.
A hierarchical database management system (HDMS) is a database management system (DBMS) that stores data in a hierarchical structure. In a hierarchical database, each data item is a child of one or more parent data items. This structure can be difficult to manage and update, and it is not well-suited for storing large amounts of data.
All of the above are DBMS types, but relational DBMS is the most common type.