This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Highest concentration of potassium is in? \nSelect and explain. \nA. Bile, B. Pancreatic juice, C. Terminal ileal secretions, D. Rectal fluid', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Colon and rectal secretion contain highest concentration of K+.', 'role': 'assistant'}]