Yup at this point its either A or C, depending on how you do LoS.
LoS comes from a base for everything, per pg 15. Terrain you use the area it takes up as the base.
Area Effect are their own enity in the game and have their own LoS. So the orginal model should not come into play.
Since we need a base for LoS, I would treat it as terrain, so the whole area it takes up as the "base." So it would be A, and there is no way to hide from area effects, except for range.