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': "Pemphigus vulgaris is characterized by all, except: \nSelect and explain. \nA. Positive Nikolsky's sign, B. Oral erosions, C. Subepidermal bulla, D. Tzanck smear showing acantholytic cells", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Pemphigus vulgaris is an intraepidermal blistering disease.', 'role': 'assistant'}]