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': 'Thimble pitting of nails is seen in \nSelect and explain. \nA. Psoriasis, B. Pemphigus, C. Lichen planus, D. Alopecia areata', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Psoriasis", 'role': 'assistant'}]