Question: In a Mobile Radio Interface Layer 3 context, what triggers the return of the 'rejectedByUser' error by the remote party in User-to-User Signalling service requests?
Option 1: Failure to obtain location information due to insufficient LCS QoS.
Option 2: Rejection of the User-to-User Signalling service request by the remote party.
Option 3: Inability to transfer requested LCS assistance data or deciphering keys for broadcast assistance data.
Option 4: Network congestion leading to a timeout in the signalling process.
Explanation: The 'rejectedByUser' error is specifically related to the remote party's action of rejecting a User-to-User Signalling service request. This error indicates that the issue lies with the user's decision at the remote end, rather than technical failures such as location information retrieval or network data transfer issues.