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': 'Zygote with zona pellucida reaches uterine cavity by : \nSelect and explain. \nA. 2 days, B. 4 days, C. 5 days, D. 6 days', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 4 days', 'role': 'assistant'}]