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': 'Water sample which is likely to contain chlorine, will affect the results of bacteriological analysis of water. Which one of the following, if added in small amount in the test tube will help overcome it – \nSelect and explain. \nA. Potassium nitrate, B. Copper sulphate, C. Calcium hydrochloride, D. Sodium thiosulphate', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]