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': 'Fluoride is least effective in which area: \nSelect and explain. \nA. Cusp, B. Pits and fissures, C. Buccal areas, D. Palatal area', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]