Which IOS features are used to avoid Routing loops when dynamic Routing protocols are used betweenPE and CE in MPLS-VPN networks？（）

A. Site Of Origin SO
B. SHAM links with OSPF
C. BGP cost community
D. BGP feature allow-as in
E. RPF Reverse Path forwarding.
F. Access-list Control in Distance Vector protocol like RIP and EIGR