Which of the following is NOT an example of a version control system?

A version control system is a tool that helps software developers manage changes to source code over time. It allows multiple contributors to work on a project simultaneously, keeps track of changes made, and enables the ability to revert to previous versions if necessary.

GitHub is an online platform that uses Git as its version control system, allowing users to collaborate on projects effectively. Mercurial is another distributed version control system similar to Git, designed for efficient handling of source code changes. Subversion is a centralized version control system commonly used in various development workflows.

Photoshop, on the other hand, is primarily a graphic design software application. Although it may include features for saving and managing different versions of files, it does not function as a dedicated version control system for source code. Therefore, it does not provide the same capabilities that a version control system offers, such as branching, merging, and tracking history related to code changes.

In summary, Photoshop does not fall under the definition of a version control system, making it the correct choice in identifying which option is not an example of such a system.