Cute chipmunk. Little bit soft. I like the color in the bg. That's very nice. As for the 'S' curve part of the challenge, I'm guessing the 'S' is the stripes on the chipmunk (like a backwards 'S')? Ideally, this challenge is more about using a curving line that leads the viewer thru the image, from a depth perspective, not really just about finding a 'S' as in the letter. All JMO of course. Good luck in the challenge.
You could use a lot tighter crop on this and really showcase the chipmonk IMO. he's very cute and appears to be in nice crisp focus - a nice square crop with his eyes in the upper third would do wonders.
I don't really see the leading line here. I would guess the tail, but its so small and doesn't grab my attention well enough to lead me. If its the rock its just too 50/50 with the back ground and doesn't lead me either.