Question: What is the primary purpose of the EFVBSCA (Voice Broadcast Service Ciphering Algorithm) file in a USIM application, as related to service n°65 being 'available'?
Option 1: To store the Master Group Key (V_Ki) for each VBS group subscribed to by the user.
Option 2: To contain the ciphering algorithm identifiers for each Master Group Key of each VBS group subscribed to by the user.
Option 3: To define the available Voice Broadcast Services (VBS) for the subscriber.
Option 4: To encode the EFVBS file contents with a specific ciphering algorithm.
Explanation: The correct answer, Option 2, accurately reflects the primary purpose of EFVBSCA. It highlights that when service n°65 is 'available', this file must be present and contains ciphering algorithm identifiers for each Master Group Key (V_Ki) of the VBS groups the user has subscribed to, complementing the definitions found in EFVBS.