Which Cisco MCU feature allows a video participant to dial in to view permanent and active conferences and select a conference to join, or allow them to create a new conference?

Ad hoc conferencing refers to the automatic creation of a conference when participants dial each other directly, not a menu-driven interface for browsing and selecting from available conferences.

ACD (Automatic Call Distribution) is a call center technology for routing inbound calls to available agents and has no role in video conferencing participant menus or conference selection.

Auto Attendant on the Cisco MCU acts as an interactive lobby service - when a participant dials the MCU, it presents a list of permanent and active conferences. The participant can navigate the menu to select and join an existing conference or initiate a new one, making it the only feature that satisfies both the browsing and creation requirements described.

A preconfigured participant is a pre-defined endpoint or dial-out entry stored within a conference configuration, not a feature that enables participants to browse or select conferences.