This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Introduction and gametogenesis., Subject name: Anatomy
[{'content': 'Morula reaches uterus at \nSelect and explain. \nA. 3rd day after feilization, B. 4th day after feilization, C. 6th day after feilization, D. 8th day after feilization', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Morula is 16 cell structure and reaches uterus by 4th day of feilisation. Soon divisions occurs and blastocyst is formed which is 64 celled structure by day 6.', 'role': 'assistant'}]