Which statement is true of a source that wants to transmit multicast traffic to group 239.1.1.1？（）

• A、Before sending traffic, it must first join  multicast group 239.1.1.1 by sending an IGMPv2 membership report to the default router on the local subnet.
• B、It must send an IGMPv2 Request to Send  packet and then wait for an IGMPv2 Clear to Send packet from the IGMPv2 querier router on the local subnet
• C、It may begin transmitting multicast traffic to the group only when there is no other host transmitting to the group on the local subnet.
• D、It may transmit multicast traffic to the group at any time.