Question: What should a UE operating in CS/PS mode 1 or CS/PS mode 2 of operation do when it is already attached to both EPS and non-EPS services and needs to detach from non-EPS services?
Option 1: Perform a separate detach procedure for each service.
Option 2: Use the combined tracking area updating procedure.
Option 3: Perform a combined detach procedure.
Option 4: Ignore the detachment request.
Explanation: According to the text, UEs that operate in CS/PS mode 1 or CS/PS mode 2 of operation and are already attached to both EPS and non-EPS services shall perform a combined detach procedure in order to detach for non-EPS services. This ensures that the UE properly detaches from non-EPS services while maintaining its attachment to EPS services.