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: Pharmacology
Opioid that activates monoamine action is: 
Select and explain. 
A. Tramadol, B. Pentazocine, C. Pethidine, D. Meperidine
A: Tramadol
Answer: A: Tramadol 
Explanation: None