Question: What does the 'uUS-Required' identifier signify in the context of requesting a service in a mobile radio interface?
Option 1: It indicates whether User-to-User Signalling (UUS) is mandatory or not required for the requested service.
Option 2: It specifies the type of location notification (e.g., notification or privacy verification) for the UUS service.
Option 3: It determines the priority level of the UUS service request in the network.
Option 4: It identifies the sender's location to the recipient in a UUS message.
Explanation: The 'uUS-Required' identifier indeed refers to whether UUS (User-to-User Signalling) is required or not when requesting the service, impacting how it's handled and delivered in mobile networks.