How could you check for potential MTU size issues on the path taken by a PE-to-PE LSP?

A.
Because MPLS packets are label switched, MTU problems can only be detected by the user applications.

B.
Use the ping vrf command with packet size set to the largest MTU along the path and DF bit set from the local PE-router to ping the remote PE-router.

C.
Use the ping vrf command with packet size set to the smallest MTU along the path and DF bit set from the local PE-router to ping the remote PE-router.

D.
Because MPLS packets are label switched, packets are automatically fragmented and reassembled by the PE-routers.
Therefore, there are no potential MTU issues.