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: Radiology
[{'content': 'A radio-opaque mass continuous with the cementoenamel junction attached to the distal surface of the first premolar is: \nSelect and explain. \nA. Hyper Keratosis, B. Calculus, C. Food debris, D. Epithelial attachment', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]