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': "Casal's paint necklace is caused by: \nSelect and explain. \nA. Lichen planus, B. Pellagra, C. Pernicious anemia, D. SLE", 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Pellagra', 'role': 'assistant'}]