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': 'Each kidney contains about -- nephrons ? \nSelect and explain. \nA. One million, B. Two million, C. Four million, D. 5 million', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e., One million', 'role': 'assistant'}]