Question: In an ISIM application, what is the primary purpose of the first record in the EFIMPU (IMS Public User Identity) during emergency scenarios or when no explicit selection is made?
Option 1: To store a secondary SIP URI for fallback purposes
Option 2: To serve as the default SIP Identity (SIP URI) for the user
Option 3: To hold a temporary SIP URI for a single session
Option 4: To contain an empty record for future assignments
Explanation: The first record in EFIMPU is designated to be used as the default SIP Identity when performing emergency registration or when no other record is explicitly selected. This ensures that there is always a valid SIP URI (User Equipment's IP Multimedia Services identity) available for communication, highlighting its role in maintaining seamless connectivity in telecom networks, especially during critical situations like emergencies.