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': "In which segment of the nephron does tubular fluid has the highest osmolarity? \nSelect and explain. \nA. Henle's loop, B. Distal tubule, C. Proximal tubule, D. Collecting duct", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]