How does a core LSR operating in the default frame mode advertise labels?

A.
The core LSR advertises a label for every destination in its FIB.

B.
The core LSR only advertises labels for destinations inside the MPLS domain.

C.
The core LSR only advertises labels for destinations outside the MPLS domain.

D.
The core LSR does not advertise labels. Label advertisements is only done by the PE-router.

Explanation:

Core LSRs receive this labeled packet and use label forwarding tables to exchange the inbound label in the incoming packet with the outbound label corresponding to the same FEC.
Reference: MPLS and VPN Architectures (Ciscopress) page 25