Damn near perfect, only the bottom one that the ellipse seems to be a bit lower than the center of the sphere, witch is not wrong per say, sometimes you do want to make the cut a bit lower, but it has to be intentional.
It doesn't have to be perfect, just good enough to fool our brains to think it is. In this case 1 and 2 looks pretty good to me so nothing to say about em besides good work!
The thing with 3 is that the distance of B does not match, so the cut seems to be lower as shown in the first example. To "fix" this there's two ways shown on Fig.1 and Fig.2.
On Fig.1 you can maintain the thickness of the ellipse but you must centralize it to make B=B.
But if you want the ellipse to be closer to the edge then you must make it thicker and try to make the distance of B match, like on Fig.2.
But overall really good work on the exercice, the circles themselves looks crispy as hell!