Question: What triggers the UE to enter the EMM-DEREGISTERED state when it is switched on?
Option 1: The UE receives a detach request from the MME.
Option 2: The UE's periodic tracking area update timer expires while in EMM-IDLE mode for emergency bearer services.
Option 3: The UE initiates an attach request to the MME, which is then accepted.
Option 4: The UE automatically enters this state upon being switched on.
Explanation: According to the provided text, one of the conditions for entering the EMM-DEREGISTERED state in the UE is when "the UE is switched on". This indicates that simply powering on the UE will cause it to enter this state, without requiring any additional actions or messages from the MME.