In a secure network topology, which of the following shows where an e-commerce Web server should be placed?

A VPN (Virtual Private Network) is used to create a secure connection over a public network, typically for remote users or site-to-site connectivity, not as a placement zone for public-facing servers.

A subnet is a logical division of an IP network; while a DMZ is often implemented as a subnet, merely stating "within a subnet" does not convey the security isolation required for public-facing servers.

A VLAN (Virtual Local Area Network) is a logical grouping of network devices that allows them to communicate as if they were on the same LAN segment, even if they are physically on different network switches; it's a segmentation method but doesn't inherently provide the same level of external isolation as a DMZ.

A DMZ (Demilitarized Zone) is a perimeter network that protects an organization's internal local-area network (LAN) from untrusted external traffic. Placing an e-commerce web server, which must be publicly accessible, in a DMZ allows it to serve internet requests while providing an additional layer of security by separating it from sensitive internal resources.