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: Pathology
[{'content': 'Dark radiolucent shadows appearing at the neck of teeth, most obvious on the mesial and distal aspect: \nSelect and explain. \nA. Radiation caries, B. Rampant caries, C. Early childhood caries., D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]