Question: What is the nature of supporting 'mo-VoiceCall establishment cause for mobile originating MMTEL voice' in a User Equipment (UE) as per E-UTRA specifications?
Option 1: Mandatory, as outlined in the Radio Resource Control (RRC) protocol specification.
Option 2: Optional, with implementation details specified in the RRC protocol specification.
Option 3: Conditional, dependent on the UE's support for a specific technical standard.
Option 4: Not Applicable, as MMTEL voice is not part of E-UTRA.
Explanation: The correct answer is Option 2 because it is explicitly stated that supporting 'mo-VoiceCall establishment cause for mobile originating MMTEL voice' is optional for UEs, indicating flexibility in implementing this feature within the E-UTRA framework.