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': 'Wha is HTH? \nSelect and explain. \nA. Hormonal contraceptive, B. Water disinfectant, C. Insecticide, D. Rodenticide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: High test Hypochlorite (HTH) or perchloron is a calcium compound which contains 60 to 70 % available chlorine for disinfection. Ref: Park 21st edition, page 661.', 'role': 'assistant'}]