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: Surgery
Which one of the opioid has maximum plasma protein binding capacity: 
Select and explain. 
A. Morphine, B. Sufentanil, C. Fentanyl, D. Pethidine
B: Sufentanil
Answer: B: Sufentanil 
Explanation: Protein binding capacity of opioids: Morphine: 30-40%., Pethidine: 70%, Fentanyl: 84%. Alfentanil: 92%., Sufentanil: 93%.