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
Ohotolidine test is used for detecting which of the following? 
Select and explain. 
A. Chlorine, B. Nitrites, C. Nitrates, D. Ammonia
A: Chlorine
Answer: A: Chlorine 
Explanation: Ohotolidine test is used for determining both free and combined chlorine in water with speed and accuracy. Ref: Preventive and Social Medicine, By K.Park, 19th edition, Page 576, 578, 579, 582