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': 'Implantation occurs at ? \nSelect and explain. \nA. 2-3 days, B. 6-7 days, C. 15-20 days, D. 20-25 days', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., 6-7 days", 'role': 'assistant'}]