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': 'Enamel knot expresses the growth factor, which can be: \nSelect and explain. \nA. Slit 1, B. FGF 4,9, C. BMP 2,4,7, D. All of the above.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]