Here's a short story: The skin on the bottom of my feet felt like they'd been shredded after cooling off at a pool for a couple of days, while the smoother surface of the second pool I enjoyed was much easier on my feet. This is because of the _____ friction of the smoother pool? (A) additional (B) reduced.  What is the most sensical answer between "smooth pool bottom" and  "course pool bottom"?
The answer to this question is:
course pool bottom