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
Water sample which is likely to contain chlorine. will affect the results of bacteriological analysis of water. %Mich one of the following, if added in small amount in the test tube w ill help overcome it ? 
Select and explain. 
A. Potassium nitrate, B. Copper sulphate, C. Calcium hydrochloride, D. Sodium thiosulphate
D: Sodium thiosulphate
Answer: D: Sodium thiosulphate 
Explanation: Ans. is 'd' i.e., Sodium thiosulphate