Jumping right in with your cylinders around arbitrary minor axes, these are generally looking good:

• Your ellipses are confidently drawn, and generally improve in their consistency over the set

• Your side edges show clear use of the ghosting method and are generally straight and smooth

• You're doing a great job of checking those minor axes in red, picking up on fairly minute mistakes, which is quite important - it's easy to plateau when we get close enough, to the point that further growth becomes difficult. You're paying close attention and continuing to milk each attempt for as much growth as you can.

• You've included a great variety of rates of foreshortening

I also wanted to mention that with all of the variety in foreshortening, I was able to see that you appear to understand (whether consciously or instinctually) how the shift in both scale from one end to the other and the shift in degree - both of them being manifestations of foreshortening - are to work in tandem. That is to say, I'm not seeing any instances where the scale shift is very dramatic, but the degree shift is limited, or vice-versa. In fact, we can see very clear examples in 95 and 89 for instance, where you've really gone overboard with the scale shift, but matched it with a very circular ellipse at the far end. Good work!

Continuing onto your cylinders in boxes, your work is similarly well done here, though with one little suggestion that I'll call out in a moment. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

As a whole you're doing great with this, and your instinctual understanding of how to handle the proportions of each box, regardless of its orientation, are developing very well and should be quite helpful as you move into the next lesson. My one recommendation however is that when you practice this exercise in the future, try and vary the rate of foreshortening on those boxes more. Right now you are definitely giving yourself a little convergence for each set of parallel edges, but they're all pretty shallow. Shaking things up with boxes that have more rapid convergence, with closer vanishing points, will help you cover a more varied assortment of situations.

Anyway, all in all, very well done. I'll go ahead and mark this challenge as complete.