Which deployment is the most scalable, manageable, and cost-effective in this scenario?

A company requires a secure wireless network to span several adjacent buildings. Employees need seamless roaming access across buildings, floors, and, potentially, outdoor areas. FortiAP devices will be used.

Which deployment is the most scalable, manageable, and cost-effective in this scenario?
A . Install FortiWiFi with a cellular modem in the buildings and areas where no wireless signal reaches from the main building.
B . Deploy a WAN connection on each building to allow FortiAP devices to communicate with FortiGate in the main building.
C . Implement a wireless mesh design to allow FortiAP devices to use neighboring FortiAP devices to connect with FortiGate in the main building.
D . Configure FortiGuard-capable FortiAP devices to broadcast the corporate SSID without being managed by FortiGate in the main building.

Answer: C