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 radiolucency associated with completely formed unerupted tooth is due to: \nSelect and explain. \nA. Impaction, B. Dentigerous cyst, C. Periodontal cyst, D. Odontogenic cyst', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]