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': 'Implantation occurs on the : \nSelect and explain. \nA. 4th day, B. 6th day, C. 3th day, D. 8th day', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 8th day', 'role': 'assistant'}]