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: Psychiatry
In patients of substance-abuse, drugs used are: 
Select and explain. 
A. Naltrexone, B. Naloxone, C. Clonidine, D. All
D: All
Answer: D: All 
Explanation: A i.e. Naltrexone; B i.e. Naloxone; C i.e. Clonidine