What is true about the MTU on an interface when running MPLS?

What is true about the MTU on an interface when running MPLS?

A.
The MTU is automatically decreased on WAN interfaces.

B.
Some switches do not support jumbo frames.

C.
If the MTU is increased on a LAN interface it can result in jumbo frames.

D.
The IP MTU is automatically decreased on LAN interfaces.