Which of the following is a networking topology concept used when placing publicly accessible hosts on a network?

VPN (Virtual Private Network) is used for securely extending a private network across a public network, primarily for secure remote access, not for placing publicly accessible hosts.

PAT (Port Address Translation) is a form of Network Address Translation (NAT) that allows multiple private IP addresses to share a single public IP address, which is a translation mechanism, not a network topology concept for publicly accessible hosts.

VLAN (Virtual Local Area Network) is used to logically segment a single physical network into multiple broadcast domains, but it's not primarily a topology concept for exposing public hosts.

A DMZ is a physical or logical subnetwork that contains and exposes an organization's external-facing services to an untrusted, larger network, usually the internet. It acts as a buffer zone between the internet and the internal local area network (LAN), allowing public services like web servers or mail servers to be accessible from outside while providing an additional layer of security for internal resources.