What is the role of Forwarding Equivalence Class （FEC） in MPLS？（）

A.FEC determines how IP packets are forwarded in MPLS LSP.
B.FEC determines how to establish an LSP path.
C.FEC determines how a group of IP packets are mapped to an LSP.
D.FEC determines how MPLS labels are stacked in LSP.
E.None of above.