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: Dental
Which of the following is not a method of chlorination of water: 
Select and explain. 
A. Perchloron, B. Ozonation, C. Chlorine gas, D. Chloramine
B: Ozonation
Answer: B: Ozonation 
Explanation: None