This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': "To find out whether teh w ater has been properly chlorinated, the test used is - \nSelect and explain. \nA. Horrock's test, B. Oho-toluidine test, C. Presumptive coliform test, D. Total bacterial count", 'role': 'user'}, {'content': 'Answer: B \nExplanation: After chlorination,tge residual chlorine is tested at the end of one hour contact period.If free residaul chlorine level is less than 0.5 mg/litre, the chlorination procedure should be repeated before water is drawn.Reagent used in OT test is analytical grade ohotoluidone dissolved in 10% hydrochloric acid.On addition of reagent to water containing chlorine it turns yellow. Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 718', 'role': 'assistant'}]