Question: For Supplementary Services like Call Barring that offer a subscription option for password control, what is required for actions such as registration, erasure, activation, or deactivation by the mobile subscriber?
Option 1: A one-time authentication token sent to the User Equipment (UE)
Option 2: Concurrent entry of a Personal Identification Number (PIN) associated with the UE's SIM card
Option 3: Approval from the network administrator via a separate communication channel
Option 4: Concurrent entry of a specific password designated for controlling that Supplementary Service
Explanation: This is correct because, according to the provided context, when a subscriber selects the option to use a password for controlling a Supplementary Service like Call Barring, every action related to that service requires the concurrent entry of this designated password. This ensures an additional layer of security and control for the subscriber over the service's management.