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
Naltrexone is used for which of the following poisoning ? 
Select and explain. 
A. Heroin, B. Atropine, C. Cannabis, D. Diazepam
A: Heroin
Answer: A: Heroin 
Explanation: None