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