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': 'Amount of blood in heart: \nSelect and explain. \nA. 250-300 ml, B. 500-600 ml, C. 1-2 litre, D. 100-200 ml', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Heart contains 12% of total blood volume; i.e. 12% of 5 Ltr = 600 ml.', 'role': 'assistant'}]