Question: For EAP-AKA' authentication, how is the username part of the Fast Re-authentication NAI modified according to IETF RFC specifications?
Option 1: The username part is appended with the single digit "4".
Option 2: The username part is prepended with the single digit "8".
Option 3: The username part remains unchanged for EAP-AKA' authentication.
Option 4: The username part is suffixed with the MCC of the Selected PLMN.
Explanation: According to specifications, for EAP AKA', the Fast Re-authentication NAI must comply with relevant standards except that the username part is specifically required to be prepended with the single digit "8", distinguishing it from EAP-AKA. This modification is crucial for correctly identifying and processing the authentication type in telecom networks.