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: Skin
[{'content': "Which of the following is NOT a primary skin disease? \nSelect and explain. \nA. Reiter's syndrome, B. Bowen's disease, C. Psoriasis, D. Lichen planus", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Reiter's syndrome", 'role': 'assistant'}]