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: Biochemistry
[{'content': 'A buffer that is most effective at a pH of about 4.5 is - \nSelect and explain. \nA. Acetate buffer, B. Bicarbonate buffer, C. Phosphate buffer, D. Tris buffer', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A buffer system is most effective when the pH of the system is near its pka value.', 'role': 'assistant'}]