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: Forensic Medicine
A 28-year-old male patient is brought to casualty in comatose state with pin-point pupils, reduced respira- tory rate and bradycardia. Most likely diagnosis: UPSC 09; CMC (Vellore) 14 
Select and explain. 
A. Tricyclic antidepressant poisoning, B. Opioid poisoning, C. Benzodiazepine poisoning, D. Organophosphorus poisoning
B: Opioid poisoning
Answer: B: Opioid poisoning 
Explanation: Ans. Opioid poisoning