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': 'Pterygium of nail is characteristically seen in – \nSelect and explain. \nA. Lichen planus, B. Psoriasis, C. Tinea unguium, D. Alopecia arcata', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pterygium is the prolongation of proximal nail fold on to the nail bed. Pterygium is diagnostic for Lichen planus.', 'role': 'assistant'}]