A. A router that pops a label from a label stack forwards a frame based on the label that was popped.

B. A router that pops a label from a label stack forwards a frame based on the underlying destination IP address.

C. A router that pops a label from a label stack applies class of service based on the IP header to ToS bits.

D. A router that pops a label from a label stack always pushes a new label on the packet