Refer to the exhibit. 

A collaboration engineer is troubleshooting a cluster that has been configured to use RSVP. The calls are being rejected and the caller receives a busy tone. What is the root cause of this problem? 

Answer options:

A. The RSVP Agents are only using an Ipv6 address.
B. IP Addressing mode preference for signaling is set to use System Default.
C. RSVP relationship between Main and Remote is set to Mandatory
D. IP Addressing Mode is set to use Ipv4 and Ipv6

A