Why is the OSPF super-backbone needed in MPLS VPN environments?

The VPN named my_vpn is operating on interface s0/0 of a PE-router. The CE-PE routing protocol is OSPF.
Why is the OSPF super-backbone needed in MPLS VPN environments?

A.
To ensure that the customer’s OSPF traffic has priority over the backbone OSPF routing updates.

B.
To ensure that the backbone internal OSPF routes are not inserted as external OSPF routes into the customer’s VPN.

C.
To ensure that the customer’s internal OSPF routes on one site are not inserted as external OSPF routes into other sites on the same VPN.

D.
To ensure that the customer’s internal OSPF routes are not inserted as external OSPF routes into the provider backbone as internal OSPF routes.