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
[{'content': "At higher concentration flouride is bactericidal, because: \nSelect and explain. \nA. It's action on bacterial enzymes., B. It coagulates the bacterial proteins., C. It destroy the bacterial cell wall, D. All of the above.", 'role': 'user'}, {'content': 'Answer: A \nExplanation: At higher concentrations, fluoride is bactericidal, because of its action on two bacterial enzymes enolase and phosphoglucomutase.', 'role': 'assistant'}]