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: Medicine
High oral: Parenteral activity ratio is seen with - 
Select and explain. 
A. Morphine, B. Diacetyl morphine, C. Oxymorphine, D. Methadone
D: Methadone
Answer: D: Methadone 
Explanation: None