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: Anatomy
[{'content': 'Which of the following has important role in initiation and maintenance of primitive streak - \nSelect and explain. \nA. FGF - 8, B. BMP - 4, C. EGRF, D. Nodal gene', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]