This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Psoriasis, Subject name: Skin
[{'content': 'Most common site affected by psoriasis is? \nSelect and explain. \nA. Flexor surface, B. Extensor surface, C. Palms and soles, D. Oral mucosa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ANSWER: (B) Extensor surfaceREF: Rook\'s textbook of dermatology 7th e p. 35.1"Most commonly involved areas in psoriasis is Extensor aspect of knees, elbows & Scalp"', 'role': 'assistant'}]