The Testking Corporation consists of the head office in New York with its regional offices in: Chicago, Detroit, Philadelphia, Toronto, and Atlanta. These offices need to be connected in a WAN, and Testking wishes to do this via a hub and spoke arrangement that will utilize packet-switched technology.Which one of the WAN technologies below would be the best choice for Testking?（）

• A、ISDN
• B、Wireless
• C、Frame Relay
• D、T1 leased line
• E、ATM
• F、VPN