Answer: WiMax (Worldwide Interoperability for Microwave Access)
Explanation: Worldwide Interoperability for Microwave Access(WiMax) is the technology with the wireless broadband that helps in the long distance communication.
The base station in WiMax is installed in the area of the service provider and the receivers are placed at the client's outlet.Thus, WiMax is used for the connection of the three offices as it can connect offices with the range of 3 miles and provides the connectivity with the speed upto 75 Mbps