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
Following are true regarding chlorination except ? 
Select and explain. 
A. Residual chlorine is 0.5 mg/lit., B. Contact period - 30 minute, C. Water should not be turbid, D. Chlorine demand should be estimated
B: Contact period - 30 minute
Answer: B: Contact period - 30 minute 
Explanation: Ans. is 'b' i.e., Contact period - 30 minute Contact period of 1 hour is recommended.