Question: In a 5G New Radio (NR) setup, as per the RRC protocol specification, what does a `CellGroupId` value of 0 signify for a User Equipment (UE)?
Option 1: A secondary cell group with the highest priority.
Option 2: The absence of any cell group configuration.
Option 3: A specific cell group reserved for handover procedures.
Option 4: The master cell group.
Explanation: According to the RRC protocol specification, a `CellGroupId` value of 0 is used to identify the master cell group. This distinction is crucial for a UE to understand its primary point of communication within the network, highlighting the role of CellGroupId in managing multiple cell groups efficiently in NR setups.