Question: What is the primary purpose of a Presence Reporting Area Identifier (PRA ID) in a mobile network?
Option 1: To identify a specific User Equipment (UE) device.
Option 2: To report changes of UE presence in a specific geographic area for policy control or charging decisions.
Option 3: To authenticate and authorize UE access to the network.
Option 4: To manage Quality of Service (QoS) parameters for UE sessions.
Explanation: A PRA ID is used to identify a Presence Reporting Area (PRA), which can be used for reporting changes of UE presence in that area. This information can then be used for policy control or charging decisions, as mentioned in the text. The correct answer highlights the primary purpose of a PRA ID, which is to report UE presence in a specific area.