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: Skin
[{'content': 'Least common site involvemnet in psoriasis is \nSelect and explain. \nA. Scalp involvement, B. Nail Involvement, C. CNS involvement, D. Ahritis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C. i.e. CNS involvement', 'role': 'assistant'}]