This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
[{'content': 'Tolerance develops to all of the following actions of opioid except: \nSelect and explain. \nA. Miosis, B. Analgesia, C. Euphoria, D. Nausea and vomiting', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref: Katzung 11/e p539 Tolerance cannot develop to 3Cs *Constipation *Constriction of pupil *Convulsions', 'role': 'assistant'}]