Simple points for multiple objects: a) the central point can be exchanged between 2 and 4, but not 1 and 2 or 2 and 3 since these latter two cases would allow 1 and 3 to touch, b) the central point can swap from 1 to 3, but not 2 or 4, c) the central point is non-simple for any change if the objects are 6-connected, but can move from 3 to 2 if the objects are 26-connected (note that the groups 2–3 and 1–4 intersect each other in the latter case).