Multi-Domain Authentication is the feature that should be enabled to support the requirement that the switch must be able to authenticate a single computer connected through a VoIP phone. Multi-Domain Authentication is a feature that allows an Aruba CX switch to apply different authentication methods and policies to different devices connected to the same port. For example, a VoIP phone and a computer can be connected to the same port using a single cable, but they can be authenticated separately using different credentials and assigned to different VLANs. The other options are incorrect because they either do not support multiple devices on the same port or do not provide authentication. Reference: https://www.arubanetworks.com/techdocs/AOS-CX/10.05/HTML/5200-7540/GUID-7D9E9F6E-5C2A-4F7E-BE6D-A2C3A6C7B9F9.html https://www.arubanetworks.com/assets/tg/TB_ArubaCX_Switching.pdf