A.Packet mode
B.Frame mode
C.Transparent mode
D.Channel mode
E.Tunnel mode

A.It removes the top label in the MPLS label stack.
B.It adds a top label in MPLS label stack.
C.It replaces the top label in the MPLS label stack with another value.
D.It replaces the top label in the MPLS label stack with a set of labels.
E.None of above.