If the OSPF protocol is used to connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone,which two options best describe the use of SHAM links?

A.
A sham-link is created between any twoo VPN sites that belong to the same OSPF area and share an OSPF backdoor link

B.
A sham-link is seen as an intra-area link between PE routers,an OSPF adjacency is created and database is exchanged

C.
A SHAM link is created between two directly connected PE routers so that it is preferred over the low speed backdoor door

D.
A SHAM link is part of OSPF network of MPLS-VPN provider.