Question: What triggers the SMF to initiate the N3 data transfer establishment procedure for a PDU session?
Option 1: The amount of data to be transferred or congestion in the network.
Option 2: The UE's state, either CM-IDLE or CM-CONNECTED.
Option 3: The inclusion of the Control Plane Only Indicator in the PDU session.
Option 4: The RAT type being NB-IoT and the UE having less than 2 active PDU sessions.
Explanation: According to the text, the SMF may initiate the N3 data transfer establishment procedure based on the amount of data to be transferred or due to congestion in the network. This is a specific condition that triggers the SMF's action, making it the correct answer.