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
Periochip is a commercially available local drug delivery system containing: 
Select and explain. 
A. Doxycycline, B. Chtorhexidine, C. Minocycline, D. Metronidazole
B: Chtorhexidine
Answer: B: Chtorhexidine 
Explanation: None