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 function in opioid addiction ? 
Select and explain. 
A. Prevention of relapse, B. Treatment of withdrawal, C. Treatment of overdose, D. Prevention of withdrawal
A: Prevention of relapse
Answer: A: Prevention of relapse 
Explanation: None