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.

A.Wait-to-Restore，F(xiàn)orced Switch，Manual Switch，Lockout of Protection
B.Manual Switch，Wait-to-Restore，Lockout of Protection，F(xiàn)orced Switch
C.Lockout of Protection，F(xiàn)orced Switch， Manual Switch，Wait-to-Restore
D.Lockout of Protection，Manual Switch， Forced Switch，Wait-to-Restore
E.Wait-to-Restore，Manual Switch，F(xiàn)orced Switch，Lockout of Protection
F.Wait-to-Restore，Manual Switch，Lockout of Protection，F(xiàn)orced Switch