Question: Who selects the Iu U-plane frame protocol mode for a given Radio Access Bearer (RAB) in the UTRAN architecture?
Option 1: Core Network (CN)
Option 2: Radio Network Controller (RNC)
Option 3: Node B (Base Station)
Option 4: User Equipment (UE)
Explanation: The selection of the Iu U-plane frame protocol mode is a function of the Core Network (CN), as it determines the operational mode for bearers, impacting data transmission between the Radio Access Network and the Core Network.