This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Water, Subject name: Social & Preventive Medicine
Select the inappropriate statement about Chlorination of water 
Select and explain. 
A. Chlorine best act at pH 7.2 of water, B. The minimum recommended concentration of free chlorine is 0.5 mg/L for one hour, C. Hypochlorous acid play main role in disinfection, D. Chloroscope instrument is used to measure residual chlorine
A: Chlorine best act at pH 7.2 of water
Answer: A: Chlorine best act at pH 7.2 of water 
Explanation: Chlorine best act at as a a disinfectant when the pH of water is7 because of predominance of Hypochlorous acid. 2.5mg bleaching powder can disinfect 1000 L of water. Chlorine has no effect on spores, cyst, ova, Hep. A, Polio virus, cyclopes. Remaining all options given are true.