Question: What is the primary purpose of the EFVGCSCA file in a USIM application, as related to Voice Group Call Service?
Option 1: To store the ciphering algorithm identifiers for each Master Group Key (V_Ki) of subscribed VGCS groups.
Option 2: To manage user subscriptions to different voice call services.
Option 3: To contain coding schemes for voice call transmissions.
Option 4: To authenticate users for group calls.
Explanation: The correct answer is Option 1 because the EFVGCSCA file specifically contains ciphering algorithm identifiers, which are crucial for securing (through encryption) the Master Group Keys of each Voice Group Call Service (VGCS) group that a user is subscribed to. This directly relates to the security and confidentiality of voice group calls, making Option 1 the most accurate choice in the context of telecom network security and USIM application functionality.