What is most likely the cause of this issue?

Your customer has an EX60 at a home-office that is doing direct H.323 dialing. When they place calls to remote sites, they report that they cannot see video or hear audio from the remote sites.

What is most likely the cause of this issue?
A . NAT mode is not configured on the EX60.
B . The HDMI cable that connects the EX60 to the monitor is not plugged in.
C . A username and password must be configured on the EX60.
D . QoS is not properly configured on the EX60.

Answer: A