For which two reasons music on hold fail to play?

A.	For which two reasons music on hold fail to play?
B.	The DRAM is corrupted on the Cisco IOS router.
C.	Analog lines terminated into the Voice gateway.
D.	Uncast music on hold is configured and IP addressing mode is set to IPV4 only.
E.	IPV4 addressing is in use.
F.	Multicast music on hold is configured and the IP addressing mode is set to IPV6 only.