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 disclosing agent 
Select and explain. 
A. Erythrocin, B. Cetyl pyridinim chloride, C. Mercurochrome, D. Two tone solution
B: Cetyl pyridinim chloride
Answer: B: Cetyl pyridinim chloride 
Explanation: None