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
An unknown patients presents with his pyrexia, constricted pupils, hypotesion, cyanosis and stupor progressing to coma. Poisoning is due to: 
Select and explain. 
A. Phenobarbitone, B. Cannabis, C. Dhatura, D. Diphenhydramine
A: Phenobarbitone
Answer: A: Phenobarbitone 
Explanation: A i.e. Phenobarbitone Among the given four options, only Phenobarbitone (Barbiturate)Q can cause constricted pupils.