- DB/2: This is a database management system (DBMS) developed by IBM.
- OS/2: This is not a DBMS; it is an operating system.
- ORACLE: This is a widely used relational database management system (DBMS).
- MS-EXCEL: While Excel is not strictly a traditional DBMS, it does have limited database-like capabilities, often used for managing small data sets. However, it is not classified as a DBMS.
Therefore, the correct answer is 2. OS/2.