Question: When does the Mobile Station (MS) include the Additional Update Type Information Element (IE) in a message?
Option 1: During a Location Area Updating procedure for circuit-switched services.
Option 2: When initiating a combined Routing Area updating procedure for GPRS services and "SMS-only service".
Option 3: During a Periodic Routing Area Updating procedure for packet-switched services.
Option 4: When responding to a Network-initiated Routing Area Updating procedure.
Explanation: The correct answer is Option 2 because the Additional Update Type IE is included by the MS when it initiates a combined Routing Area updating procedure specifically for GPRS services and "SMS-only service", as stated in the specification. This ensures that the network is informed about the type of update being performed, which is essential for proper routing and service handling.