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 to scan networks, discover live hosts, identify open ports, and fingerprint services and operating systems. It is the canonical tool for network target enumeration in both penetration testing and security assessments. Its breadth of scan types and scripting engine make it uniquely suited for identifying potential targets across an entire network range.

NIKTO is a web server vulnerability scanner that probes HTTP/HTTPS services for known issues, not a general-purpose network host discovery tool.

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

John the Ripper is a password-cracking tool used to crack hashed credentials offline, not a network scanning utility.