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
Least common site involvemnet in psoriasis is 
Select and explain. 
A. Scalp involvement, B. Nail Involvement, C. CNS involvement, D. Ahritis
C: CNS involvement
Answer: C: CNS involvement 
Explanation: C. i.e. CNS involvement