Question: What is the primary purpose of the GUTI reallocation procedure in EPS?
Option 1: To update the UE's TAI list and DCN-ID.
Option 2: To allocate a new GUTI to a particular UE, optionally providing a new TAI list, DCN-ID, or UE radio capability ID.
Option 3: To initiate the attach procedure for a UE in EMM-REGISTERED state.
Option 4: To perform implicit reallocation of a GUTI during tracking area updating procedures.
Explanation: The correct answer is Option 2 because the primary purpose of the GUTI reallocation procedure is to allocate a new GUTI to a particular UE, and optionally provide additional information such as a new TAI list, DCN-ID, or UE radio capability ID. This is stated in the text as "The purpose of the GUTI reallocation procedure is to allocate a GUTI and optionally to provide one or more of the following to a particular UE...".