Question: When does the Mobile Station (MS) include the TMSI Status Information Element (IE) in a message?
Option 1: When the MS has a valid Temporary Mobile Subscriber Identity (TMSI) and performs a location area update.
Option 2: When the MS performs a combined routing area update and no valid TMSI is available.
Option 3: When the MS has an invalid TMSI and performs a periodic routing area update.
Option 4: When the MS has a valid TMSI and performs a detach procedure.
Explanation: The correct answer is Option 2 because, according to the specification, the TMSI Status IE is included when the MS performs a combined routing area update and no valid TMSI is available. This ensures that the network is informed about the MS's TMSI status during this specific procedure.