Why would an endpoint stop sending 720p in a call with a Cisco TelePresence MCU?

A.
Another endpoint failed in its negotiation with the Cisco TelePresence MCU.

B.
The endpoint Ethernet speed renegotiated at half-duplex.

C.
The Cisco TelePresence MCU is using video to receive bit rate optimization to request a
lower bandwidth.

D.
Another endpoint joined the conference, which brought the conference rate down.