Apple 9L0-S02 Question

I've just completed this exam, I did fairly well but this question has me miffed.

What are the regional variation of the bottom cover of MacBook Pro (Retina, Mid 2012) and (Retina, 15-inch, Early 2013, Late 2013)?

I have gone through all the information that I have butI can not find an answer, does anyone have a clue?

Thanks