Question: What is the prerequisite for executing NAS procedures between the UE and the MME?
Option 1: A valid IP address must be assigned to the UE.
Option 2: A NAS signalling connection must exist between the UE and the MME.
Option 3: The UE must be in a specific state, such as idle or connected.
Option 4: The MME must have knowledge of the UE's location.
Explanation: For NAS procedures to be executed between the UE and the MME, a signalling connection must be established. This is because NAS signalling is used for control plane functions, such as session management and mobility management, which require a dedicated signalling channel.