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

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

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

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

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

E.
None of above