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
To find out whether the water has been properly chlorinated, the test used is – 
Select and explain. 
A. Horrock's test, B. Ortho–toludine test, C. Presumptive coliform test, D. Total bacterial count
B: Ortho–toludine test
Answer: B: Ortho–toludine test 
Explanation: None