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': 'Pulpal infection in primary mandibular posterior teeth is\nfirst manifested on a radiograph in the area? \nSelect and explain. \nA. Of bifurcation, B. At the apex of the root, C. Around the permanent tooth bud, D. Near the crest of alveolar bone', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]