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: Skin
[{'content': 'Least common site involvement in psoriasis is: \nSelect and explain. \nA. Scalp involvement, B. Nail involvement, C. CNS involvement, D. Arthritis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. c. CNS involvementScalp is a common site of involvement in psoriasis. Corona psoriatica is a band of psoriasis, projecting beyond hairline on forehead.Nail changes in psoriasis are pitting, onycholysis, subungual hyperkeratosis, splinter hemorrhages, uneven surface.', 'role': 'assistant'}]