Refer to the exhibit.

The SD-WAN 7.6 Enterprise Administrator Study Guide states: “An SD-branch is a site with an SD-WAN spoke FortiGate device and one or multiple extensions.” It explains that FortiSwitch and FortiAP provide wired and wireless LAN connectivity through FortiLink, while FortiExtender supplements WAN connectivity by providing 4G/5G transport.

The guide further explains that the management plane sees extension-device ports as logical interfaces belonging to the controlling FortiGate. Therefore, FortiSwitch, FortiAP, and FortiExtender do not become independent SD-WAN topology nodes and do not require separate topologies. FortiGate devices with FortiLink connections also do not need to be excluded.

FortiExtender is specifically designed as a natural SD-WAN extension that introduces cellular connectivity as another WAN transport. Consequently, a FortiGate using FortiExtender can function as a hub, provided it satisfies the required capacity, routing, and IPsec design requirements. There is no rule requiring hubs to be extension-free. Therefore, option D correctly describes the unified topology shown in the exhibit.