Hipopalamus

This http://i.imgur.com/UrBeIyg.png is a picture of a T2 mri scan of the head. The white/gray represents parts of the head with more fluid and the darker parts with less fluid. Therefore, the skull is dark and the brain gray and parts like the skin is white (to my understanding...I may be wrong). My question: please identify A, B and C. Is A or C the scalp. I have been assuming that A is the scalp/ skin, but I have been wondering if A is an artifact of the mri image processing (keep in mind all of the head mri's I have have this)... If A is the scalp why is there a black/dark space B between A and C. Your help is much appreciated. Thanks