The network administrator must complete the connection between the RTA of the XYZ Company and the service provider. To accomplish this task, which two devices could be installed at the customer site to provide a connection through the local loop to the central office of the provider (Choose two.)（）。

• A、WAN switch
• B、PVC
• C、ATM switch
• D、multiplexer
• E、CSU/DSU
• F、modem