Question: In which of the following scenarios may a serving network establish an emergency call without applying the security mode procedure?
Option 1: When the UE has a valid (U)SIM and the serving network has obtained authentication vectors.
Option 2: When the UE is roaming in a network with which it has a roaming agreement.
Option 3: When the (U)SIM is absent, making authentication impossible.
Option 4: When the serving network has successfully authenticated the (U)SIM but the user is not authorized for emergency services.
Explanation: According to the security procedures outlined in 3GPP TS 33.102, a serving network may establish an emergency call without applying the security mode procedure when authentication is impossible due to the absence of a (U)SIM. This ensures that users can still make emergency calls even if they do not have a valid SIM card or if their SIM card is not permitted to receive non-emergency services from the serving network.