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: Gynaecology & Obstetrics
[{'content': 'Syncytiotrophoblasts and cytotrophoblasts differentiate on what day after the feilization? \nSelect and explain. \nA. 6 days, B. 8 days, C. 10 days, D. 12 days', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 8 days', 'role': 'assistant'}]