>>10310363Noticed how every single circle dividing line in the bigger picture is either orthogonal or parallel to each other? I think you can already clrearly exclude c and e with that, where the axis seem to be quite random. Now look at the top of the largest circle, there is a tiny line coming out. rotate the entire picture such that the line and the ball below are held fixed until the dividing axis of the larger circle and the tine line match. The fill-in part now hovers on top of the tiny black ball, which is probably to be understood as one of the moons of the fill-in medium sized ball. All medium sized balls have three moons and the number of half-circles of their moons increases by two counting clockwise, if you insert picture a. Also the number of moon-moons (yes moon-moons) increases by one counting clockwise. I think it's a.