This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Development period- week 1,2,3,4, Subject name: Anatomy
[{'content': 'How soon after feilization occurs within the uterine tube does the blastocyst begin implantation?, \nSelect and explain. \nA. Within minutes, B. By 12 hours, C. By day 1, D. By day 5', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The blastocyst begins implantation by day 5 after feilization.', 'role': 'assistant'}]