What is the BGP synchronization rule？（）

• A、Routing information received through an IBGP session is not forwarded to another IBGP neighbor， onlyto EBGP neighbors
• B、Routing information received through an EBGP session is not forwarded to another EBGP neighbor，only to IBGP neighbors
• C、BGP neighbor peerings are established and sychronized using the TCP 3-way handshake
• D、BGP shall not advertise a route until that route has been learned via an IGP also