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
[{'content': "All of the following are differential diagnosis for constricted pupils except \nSelect and explain. \nA. Horner's syndrome, B. Pontine myelinosis, C. Opioid withdrawl, D. Organophosphaste poisoning", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Opioid poisoning: Pin point pupils.\nOpioid\xa0withdrawl: dilated pupils.', 'role': 'assistant'}]