The VPN named my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protocol is RIP. The MPLS backbone IGP is OSPF. However, when you review the configuration for the PE-router, you find that BGP has been configured.
What explains this configuration?

A.
VPN routes are always imported and exported using MP-BGP.

B.
This router is configured improperly.
BGP is not needed in this configuration.

C.
This router is configured improperly.
E-BGP is the required routing protocol between PE and CE-routers.

D.
BGP should be configured on all routers supporting MPLS to ensure backward-compatibility reasons for earlier version of IOS.

Explanation:

BGP distributes reachability information for VPN-IPv4 prefixes for each VPN. BGP communication takes place at two levels: within IP domains, known as an autonomous systems (interior BGP or IBGP) and between autonomous systems (external BGP or EBGP). PE-PE or PE-RR (route reflector) sessions are IBGP sessions, and PE-CE sessions are EBGP sessions
Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1830/products_feature_guide09186a00800e977b.html#11