Question: In a USIM with service n°10 "available", when a status report is requested for an SMS but no corresponding record is found in the Elementary File for Short Messages (EFSMSR), what action does the Mobile Equipment (ME) take regarding the SMS status?
Option 1: The ME updates the SMS status to '00' (no status report requested).
Option 2: The ME leaves the SMS status unchanged.
Option 3: The ME updates the SMS status to '15' (status report requested, received but not stored in EFSMSR).
Option 4: The ME automatically deletes the SMS from the USIM memory.
Explanation: According to the specified behavior for service n°10 "available" and when a corresponding record in EFSMSR is not found, the ME must update the status of the SMS to reflect that the status report was requested but the message itself is not stored in EFSMSR. This is accurately represented by status '15'. This action ensures the USIM maintains an accurate record of message handling statuses, crucial for reliable communication and further processing of messages in telecom networks.