The correct answer is D. Located anywhere and built on IPv4 or IPv6. In Zero Trust architecture, the network and application access model is not tied to a specific physical location, branch, or data center. Zscaler's Zero Trust guidance emphasizes that users, devices, and applications can be securely connected in any location, which is a core shift away from legacy perimeter-based designs. The architecture is also described as IP independent, meaning policy and access decisions are not fundamentally anchored to traditional network constructs such as fixed addressing or trusted subnets. This is why Zero Trust can operate across modern environments regardless of where workloads reside.

The option about VPN concentrators is incorrect because VPN-based architecture is associated with legacy remote-access models that extend network trust and expose services differently from Zero Trust. In contrast, Zero Trust reduces implicit trust, avoids broad network-level access, and focuses on secure, application-aware connectivity. Therefore, the most complete and accurate answer is that a Zero Trust network can be located anywhere and built on IPv4 or IPv6, rather than being limited to a legacy transport or perimeter model.