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
Pterygium of nail is characteristically seen in – 
Select and explain. 
A. Lichen planus, B. Psoriasis, C. Tinea unguium, D. Alopecia arcata
A: Lichen planus
Answer: A: Lichen planus 
Explanation: Pterygium is the prolongation of proximal nail fold on to the nail bed. Pterygium is diagnostic for Lichen planus.