Question: What is the relationship between Anonymous Communication Rejection (ACR) and Incoming Communication Barring (ICB) in terms of their stage 3 specification?
Option 1: ACR is a distinct supplementary service with no relation to ICB.
Option 2: ACR is a special case of the incoming Communication Barring (ICB) service.
Option 3: ICB is a subset of the ACR supplementary service.
Option 4: Both ACR and ICB are unrelated, but both are forms of Communication Forwarding services.
Explanation: In the context of stage 3 specification, Anonymous Communication Rejection (ACR) is specifically identified as a special case of the incoming Communication Barring (ICB) service. This indicates that while ACR has its unique application, its underlying specifications and functionalities are derived from or closely related to those of ICB, highlighting their interconnected nature within the supplementary services framework.