Refer to the exhibit.

An enterprise is migrating its single-area OSPF network from a Frame Relay WAN service to an
MPLS L3VPN service. Frame Relay will remain in only a few sites that require increased resiliency
via two different WAN connections.
Which feature could be used in the ?MPLS VPN service provider network to support the design
requirement by ensuring that during normal operation, intersite traffic will only use the MPLS VPN
service and not the old Frame Relay service?

A.
virtual links

B.
sham links

C.
multiple stub areas

D.
super backbone