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
A buffer that is most effective at a pH of about 4.5 is - 
Select and explain. 
A. Acetate buffer, B. Bicarbonate buffer, C. Phosphate buffer, D. Tris buffer
A: Acetate buffer
Answer: A: Acetate buffer 
Explanation: A buffer system is most effective when the pH of the system is near its pka value.