Question: For an unauthenticated UE in Limited Service Mode (LSM) establishing an emergency call, what NAS protocol algorithms must the MME use, regardless of the UE's announced supported algorithms?
Option 1: EIA0 for integrity and EEA0 for ciphering
Option 2: The first available pair from the UE's list of supported algorithms
Option 3: Default MME algorithms, which may vary based on configuration
Option 4: Algorithms negotiated through an additional security context setup
Explanation: According to 3GPP security architecture, when an MME allows an unauthenticated UE in LSM to establish bearers for an emergency call, it must select EIA0 for integrity protection and EEA0 for ciphering, disregarding the algorithms previously announced by the UE, ensuring a standardized secure connection for emergency services.