What is a reason for 6PE to use two MPLS labels in the data plane instead of one?

A.
6PE allows penultimate hop popping and has a requirement that all P routers do not have to be
IPv6 aware.

B.
6PE does not allow penultimate hop popping.

C.
It allows MPLS traffic engineering to work in a 6PE network.

D.
It allows 6PE to work in an MPLS network where 6VPE is also deployed.