It's B since we know it is an equilateral triangle and since the sides are congruent, and CF are medians/bisect AB, Triangle AFO is a right triangle. Now,
8, because point O is the centroid because it is the intersection point of the medians. The distance from a vertex to the centroid is always the same, and the ratio of the distance from a vertex to the centroid to the distance from the centroid to the side is always 2:1. So, we know that since FO=4, CO=8. AO=CO, so AO=8.
