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': 'Which among the following is the most common site affected by psoriasis? \nSelect and explain. \nA. Flexor surface, B. Extensor surface, C. Palms and soles, D. Oral mucosa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In psoriasis, classically patients develop sharply demarcated red plaques (raised plateaulike lesions) with silvery white scale distributed about the scalp, trunk, and limbs, with a predilection for extensor surfaces such as the elbows and knees.', 'role': 'assistant'}]