单项选择题
You are the Cisco Network Designer in Cisco.com. Which of these is a Layer 2 transport architecture that provides packet-based transmission optimized for data based on a dual ring topology?（）
A. DynamicTrunking Protocol B. Resilient Packet Ring C. Synchronous Digital Hierarchy D. Coarse Wave Division Multiplexing
单项选择题 You are the network consultant from Cisco.com. Please point out which Layer 2 access designs does not support VLAN extensions?（）
