The correct choice is B. Using a single public IP . PAT (Port Address Translation) is a form of NAT that allows many internal private IP addresses to share one public IP address by tracking sessions with port numbers. This is one of the most common edge-network designs for homes, small offices, and many enterprise branch environments.

The reason PAT is so useful is that it conserves public IPv4 addresses. Internal hosts keep their private addressing, and when they access external resources, the firewall or router translates those connections so they appear to come from one public address, while still keeping each session unique through port mapping.

The other options are unrelated to PAT’s primary purpose. BGP is a routing protocol for route exchange between networks. Redundant ISPs deal with resiliency and multihoming, not port-based address translation. A dual-stack IP scheme means running IPv4 and IPv6 together, which is separate from the NAT/PAT function.

This question is really asking what situation most naturally calls for PAT. When an organization wants multiple internal devices to reach the internet without assigning each device its own public IPv4 address, PAT is the standard solution. That makes using a single public IP the best answer.