The S bit in the MPLS header is used for what purpose?

A.
To indicate the bottom level in the label stack

B.
To indicate if LDP is sync to the IGP

C.
To indicate if LDP is sync to the IGP

D.
To indicate the status of the LSP

Explanation:

a 1-bit bottom of stack flag. If this is set, it signifies that the current label is the last in the stack.