This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skin, Subject name: Pharmacology
[{'content': 'Which is not used in acne:(2003) \nSelect and explain. \nA. Erythromycin, B. Ampicillin, C. Clindamycin, D. Doxycycline', 'role': 'user'}, {'content': 'Answer: B \nExplanation: bRef: KDT, 5th ed, p. 800, 801 & 4th ed, p. 858s', 'role': 'assistant'}]