Which of the following open source tools would be the best choice to scan a network for potential targets?

Nmap (Network Mapper) is specifically designed for network exploration and security auditing, capable of discovering live hosts, open ports, running services, and OS details across an entire subnet. Its breadth of scanning techniques and scriptable engine make it the definitive open source tool for identifying potential targets on a network.

Nikto is a web server vulnerability scanner focused on HTTP/HTTPS services, not a general-purpose network host discovery tool.

Cain and Abel is a Windows-based password recovery and network sniffing tool, not designed for broad network scanning to enumerate targets.

John the Ripper is an offline password hash-cracking tool and has no capability to scan a network for active hosts.