Question: What happens to a PDU session with more than one QoS rule during inter-RAT idle mode mobility to NB-IoT?
Option 1: The SMF maintains all QoS rules.
Option 2: The SMF adds a new default QoS rule.
Option 3: The SMF modifies the existing QoS rules.
Option 4: The SMF initiates a PDU session modification procedure to remove non-default QoS rules and maintain only the default QoS rule.
Explanation: According to the specification, during inter-RAT idle mode mobility to NB-IoT, if a PDU session has more than one QoS rule, the SMF shall initiate a PDU session modification procedure to remove any non-default QoS rule and maintain only the default QoS rule. This ensures that the PDU session is handled correctly during the mobility event.