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: Social & Preventive Medicine
[{'content': 'Fresh bleaching powder contains \nSelect and explain. \nA. 0.33% chlorine, B. 3.3% chlorine, C. 33% chlorine, D. 0.033% chlorine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]