Question: What triggers a mobile station (MS) to leave the MM IDLE state?
Option 1: Receipt of a paging message from the network.
Option 2: Establishment of an RR connection or triggering of one of the MM procedures.
Option 3: Insertion or removal of the SIM/USIM card.
Option 4: Completion of a PLMN search.
Explanation: The MM IDLE state is left when one of the MM procedures are triggered or an RR connection is established. This indicates that any activity related to mobility management (MM) or radio resource (RR) connection establishment will cause the MS to transition out of the idle state, making option 2 the correct answer.