What is a difference between an UNI and a NNI cell header?

What is a difference between an UNI and a NNI cell header?

A.
NNI has 8 bits allocated to the VCI

B.
NNI has 8 bits allocated to the VPI

C.
UNI has 8 bits allocated to the VCI

D.
UNI has 8 bits allocated to the VPI

E.
NNI has 4 bits reserved for GFC