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: Dental
[{'content': 'Koebner phenomenon present in which of the following – \nSelect and explain. \nA. Plane warts, B. Pemphigus vulgaris, C. Lupus vulgaris, D. Lichen simplex chronicus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]