Question: In Mission Critical (MC) services, what is a prerequisite for an authorized MC service user to participate in a newly created temporary group through a group regroup operation they initiated?
Option 1: The user must be a network administrator.
Option 2: The user's device must support multiple simultaneous group affiliations.
Option 3: The user must have been an existing member of, and affiliated to, at least one of the constituent groups involved in the regroup operation and then affiliate to the new temporary group.
Option 4: The user needs to perform a full network re-registration after initiating the group regroup.
Explanation: This is because an authorized user can only participate in a temporary group they created through regrouping if they were already part of one of the groups being combined and then join the new temporary group, ensuring continuity and security in mission-critical communications by verifying the user's existing affiliation with at least one of the involved groups.