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
The minimum contact period after chlorination: 
Select and explain. 
A. 1/2 hour, B. 1 hour, C. 2 hours, D. 3 hours
B: 1 hour
Answer: B: 1 hour 
Explanation: Ans: B (I hour) Ref: Park's Textbook of Preventive and Social Medicine,20th edition, page 625Explanation:Refer to the above explanation.