Question: What happens to a UE's Access Stratum functions when it enters Power Saving Mode (PSM)?
Option 1: The UE's Access Stratum functions are activated.
Option 2: The UE's Access Stratum functions remain unchanged.
Option 3: The UE's Access Stratum functions are partially deactivated.
Option 4: The UE's Access Stratum functions are completely deactivated.
Explanation: According to the text, when a UE enters PSM, it deactivates its Access Stratum functions. This means that the UE stops all idle mode procedures, but continues to run any NAS timers that may apply. The UE's Access Stratum functions are considered as deactivated during PSM, and the MME considers the UE to be EMM_REGISTERED, but not reachable.