Which of the following is a widely used version control system?

A widely used version control system is Subversion. It serves as a tool for managing changes to source code over time, allowing developers to keep track of modifications, collaborate effectively, and maintain a history of their projects. Subversion enables users to revert files to previous states, compare changes over time, and create branches for working on features in isolation. This makes it a vital tool for software development teams to facilitate collaborative work and ensure consistency in code management.

In contrast, the other options serve different purposes. Jira is primarily a project management tool often used for issue and bug tracking, Puppet is an automation tool for managing infrastructure and configuration, and Jenkins is a continuous integration and continuous delivery (CI/CD) tool that automates parts of software development processes. While these tools are important in software development workflows, they do not function as version control systems.