Which of the following is known as an open-source database management system?

The chosen answer, MYSQL, is considered an open-source database management system because it is freely available to the public, allowing users to download, use, modify, and distribute the software without any licensing fees. This open-source nature encourages community collaboration, resulting in continual updates and improvements from users and developers around the world.

MYSQL is widely used for various applications, especially in web development, due to its ease of use, reliability, and support for various programming languages. Its open-source model not only promotes a wide range of practices and innovations but also facilitates transparency in its development and security practices, which many enterprises and developers appreciate.

In contrast, the other options represent commercial database management systems. MS SQL, Oracle, and DB2 are proprietary products that require purchasing licenses for use. They are developed and maintained by specific companies and usually come with comprehensive support and various features that cater to enterprise needs, but they do not have the same level of community-driven development or availability as MYSQL.