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: Skin
[{'content': 'Treatment of nodulocystic acne is \nSelect and explain. \nA. Erythromycin, B. Teacycline, C. Isoretinonine (Retinoic acid), D. Steroids', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Isoretinonine', 'role': 'assistant'}]