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
In 3 mix paste; discoloration occurs due to presence of: 
Select and explain. 
A. Ciprofloxacin, B. Minocycline, C. Metronidazole, D. Tetracycline
B: Minocycline
Answer: B: Minocycline 
Explanation: None