The suggested answer is B, C, D.
Network Call Deflection is a feature that relies on specific technical and regional requirements. One consideration is regional compliance, such as with ETSI Supplementary Service Network Call Deflection in Europe. Additionally, there are limitations on the functions that can be used; for example, features like announcement, collect digits, converse-on, and others cannot be utilized for NCD. Lastly, Network Call Deflection can only occur if the incoming call to the Avaya Aura Communication Manager is not answered, meaning the ISDN CONNECT message is not sent to the PSTN switch.