When you design a network, when would it be required to leak routes into a Level 1 area?

When you design a network, when would it be required to leak routes into a Level 1 area?
A. when a multicast RP is configured in the nonbackbone area
B. when MPLS L3VPN PE devices are configured in the Level 1 areas
C. when equal cost load balancing is required between the backbone and nonbackbone areas
D. when unequal cost load balancing is required between the backbone and nonbackbone areas

Answer: B