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
True statement regarding chlorination is 
Select and explain. 
A. Chlorine acts best when pH is around 7, B. Orthotolidine test measures combined chlorine separately, C. It kills bacteria, viruses and spores, D. Hypochlorite ions are mainly responsible for disinfecting activity
A: Chlorine acts best when pH is around 7
Answer: A: Chlorine acts best when pH is around 7 
Explanation: None