问题：

[多选] Which three IP multicast group concepts are true?（）

A . If a packet is sent to a multicast group address, the multicast frame contains the source multicast address.
B . A router does not have to be a member of a multicast group to recei ve multicast data.
C . A router must be a member of a multicast group to send to the group.
D . A router does not have to be a member of a multicast group to send to the group.
E . If a packet is sent to a multicast group address, all members of the multic ast group will receive it.
F . A router must be a member of a multicast group to receive multicast data.