Starting with the cylinders around arbitrary minor axes, you've largely done a good job of drawing your ellipses, keeping them aligned fairly well and identifying their 'true' minor axes to help refine your control over their orientations. All that looks solid, and is well done. One issue I am noticing however is that you've pretty consistently drawn cylinders that are extremely shallow in their foreshortening - to the point of not really having any foreshortening at all in most cases. There's basically no convergence from one end to the other, and in a few cases (132, 133, etc.) you actually end up with divergence. This tells me that you're not necessarily thinking about how foreshortening might apply to these.

Going through the set, there was only one that really stood out to me as having conscious foreshortening - 146 - and honestly it was very well executed, both with showing any foreshortening at all, but also in that it shows the appropriate shift in both scale (far end smaller than the near end) and degree (far end proportionally wider than the near end) in appropriate quantities. That is to say, having that degree not shift at all would have been incorrect, or having it shift vastly moreso would also have been wrong. You maintained the relationship between these two aspects of foreshortening very well in this one case, but there aren't really any other opportunities to assess that simply because you neglected to apply foreshortening at all throughout the rest.

Again - none of this is inherently incorrect (aside from the couple places you ended up with divergence), but more realistically you're not really ever going to end up with foreshortening so shallow that there is no visible convergence between the side edges. Keep that in mind for the future - always incorporate some convergence, and when doing any kind of exercise involving a lot of a simple form, add some variety with more dramatically foreshortened ones, shallower foreshortened ones, and anything in between.

Moving onto the cylinders in boxes, this exercise is primarily about the boxes themselves, rather than the cylinders. Similarly to how in the box challenge we incorporate line extensions to help analyze whether the box meets certain characteristics, how far off it is from meeting those characteristics, and ultimately using our awareness of those errors to gradually modify our approach for the next attempt, here we are adding the additional lines the cylinders introduce to our error checking. Where the original box has 12 extended lines, the cylinder itself adds another 6.

These lines are useful specifically in having the student build a more intuitive sense on how to draw boxes that have a pair of opposite phases that are proportionally square. This is precisely because those additional lines from the cylinders only align to the box's own vanishing points when the ellipses are themselves representing circles in 3D space. If those ellipses represent circles, then the planes containing them must also represent squares, by their very definition. So by applying the line extensions and gradually shifting our approach to bring them more in line with one another, we gradually develop an intuitive sense of how to draw boxes that will be far more useful (due to that proportionally square quality) throughout Lessons 6 and 7.

In this regard you've certainly improved a fair bit. There are some that still stand out as being more squashed or stretched, like 99, but as we progress through the set I can see a greater tendency towards making your planes square, at least on one axis. This should serve you fairly well throughout the next two lessons.

Be sure to keep the point about foreshortening in mind, but I'll go ahead and mark this challenge as complete.