This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Free Radical Injury, Subject name: Pathology
[{'content': 'Most reactive free radical is: \nSelect and explain. \nA. Superoxide, B. Hydroxyl, C. Peroxide, D. Carboxyl', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Hydroxyl radical is the most reactive free radical.', 'role': 'assistant'}]