This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autoimmune skin disorders, Subject name: Dental
[{'content': 'Oil drop is seen in \nSelect and explain. \nA. Psoriasis of nails, B. Clubbing, C. Lichen planus of nails, D. Tinea unguium', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Oil drop sign is seen in nail psoriasis IADVL textbook of dermatology page 1035', 'role': 'assistant'}]