Which of the following has the highest concentration of potassium in a normal individual?

The highest gastrointestinal concentrations of potassium are found in the colon and rectum. Under normal conditions, the colon absorbs sodium and chloride and secretes bicarbonate and potassium. Potassium secretion occurs in the distal colon. This secretion combined with potassium in bacteria and colonic mucous in stool may explain the relatively high concentration of potassium, 50-90 mmol/L, in stool. Ref: Essentials of General Surgery, 4e By Peter F. Lawrence, Richard M. Bell, Merril T. Dayton, 2006, Page 55.