In the context of MPLS, what is the correct action to be performed when an aggregate label is
received?

A.
It replaces the bottom label in the MPLS label stack with a VPN label and propagates

B.
It replaces the top label in the MPLS label stack with a VPN label and propagates

C.
It adds the VPN label into the top label in the MPLS label stack

D.
It removes the top label in the MPLS label stack and does a Layer 3 lookup on underlying IP
packets