Which command is used to add a new repository to the APT sources list?

The command used to add a new repository to the APT sources list is known as add-apt-repository. This command is part of the software-properties-common package, which includes tools for managing your software repositories in Debian-based distributions, such as Ubuntu.

When you run add-apt-repository, it effectively makes changes to the /etc/apt/sources.list file or adds a new file to /etc/apt/sources.list.d/, allowing the system to know where to find additional packages beyond those provided by the default repositories. This is particularly useful for installing software that is not available in the standard channels, such as third-party applications or newer versions of existing software.

Understanding how to use this command is essential for system administration in Linux, particularly for users who need to maintain their own software installations or manage dependencies effectively. The other options provided do not correspond to valid commands for this purpose, making add-apt-repository the correct choice.