This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Papulosquamous disorders, Subject name: Dental
[{'content': 'Grattage test is used for- \nSelect and explain. \nA. Tinea capitis, B. Lichen planus, C. Pemphigus vulgaris, D. Psoriasis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Grattage test: scales in a psoriatic plaque can be accentuated by scraping with a glass slide. signe de la tache de bougie: characteristic coherence of scales as if one scratches a wax candle', 'role': 'assistant'}]