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: Unknown
Disinfecting action of chlorine in chlorination of water is mainly due to: 
Select and explain. 
A. Hypochlorite ion, B. Chloride ion, C. Sodium chloride, D. Hypochlorous acid
D: Hypochlorous acid
Answer: D: Hypochlorous acid 
Explanation: Ref. Foundations of Community medicine. Page. 62
 
Chlorination

The disinfecting action of chlorine is predominantly due to hypochlorous acid.
Hypochlorous acid is most effective form of chlorine and it is almost 70-80 times more effective