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': 'In normal edge and centroid relationship \nSelect and explain. \nA. Edge and centroid are in one plane, B. Edge is in front of centroid, C. Edge is behind the centroid, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]