Question: What is the primary reason for the BM-SC to initiate the MBMS de-registration procedure?
Option 1: To establish a new multicast MBMS bearer service.
Option 2: To terminate a specific multicast MBMS bearer service.
Option 3: To update the session attributes of an existing MBMS bearer service.
Option 4: To add a new GGSN to the list of downstream nodes parameter.
Explanation: The BM-SC initiates the MBMS de-registration procedure when a specific multicast MBMS bearer service is terminated, as stated in the text. This procedure results in releasing all MBMS Bearer Contexts and tearing down the distribution tree for the delivery of session attributes and MBMS data.