Which of the following Linux distributions is focused on penetration and security testing?

Kali Linux is specifically designed for penetration testing and security assessments. It comes pre-installed with numerous security tools and utilities that are essential for testing network and application security. These tools include vulnerability scanners, password cracking tools, and network analyzers, making Kali a preferred choice among security professionals and ethical hackers.

The distribution is built on Debian, but unlike standard Debian, which serves general-purpose needs, Kali has a clear emphasis on security testing functionalities. This focus is reflected in its default setup, providing a robust platform for conducting security research and assessments. Therefore, the selection of Kali Linux is the most appropriate for penetration and security testing due to its tailored toolset and emphasis on security.