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': 'Which of the following is not a component of counter current multiplier mechanism? \nSelect and explain. \nA. Vasa-recta, B. Thick ascending limb of loop of Henle, C. Thin descending limb of loop of Henle, D. Collecting duct', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. Vasa-recta', 'role': 'assistant'}]