A. The LSR assigns a unique label to each FEC, but labels assigned by different LSRs do not necessarily match.

B. The LSR assigns a unique label to each FEC. and that label remains constant across the MPLS domain

C. An LSR assigns the same label to FECs with the same best next hop; labels assigned by different LSRs do not necessarily match

D. An LSR assigns the same label to FECs with the same best next hop: labels remain constant across the MPLS domain