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': 'Cells which are absent in the junctional epithelium: \nSelect and explain. \nA. Melanocytes, B. Langerhans cells, C. Merkel cells, D. None of the above.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]