Which of the following is an open-source operating system?

An open-source operating system is one whose source code is made publicly available, allowing anyone to view, modify, and distribute it. Linux is a prime example of an open-source operating system, known for its flexibility, security, and wide range of distributions.

• Windows is a proprietary operating system developed by Microsoft.
• Mac OS (now macOS) is a proprietary operating system developed by Apple for its Macintosh computers.
• iOS is a proprietary mobile operating system developed by Apple for its mobile devices like iPhones and iPads.

These proprietary systems have restricted access to their source code.