This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Gynaecology & Obstetrics
[{'content': 'Morula period is a ----- cell stage \nSelect and explain. \nA. 4 to 8 cell stage, B. 12 to 16 cell stage, C. 28 to 32 cell stage, D. 50 to 60 cell stage', 'role': 'user'}, {'content': "Answer: B \nExplanation: After feilization, the zygote is a diploid cell with 46 chromosomes, undergoes cleavage, and zygote cells produced by this division are called blastomeres. As the blastomeres continue to divide, a solid mulberry-like ball of cells, the morula is produced. The morula enters the uterine cavity about 3 days after feilization. The gradual accumulation of fluid between the morula cells leads to the formation of the early blastocyst. The morula period begins at the 12- to 16cell stage and ends when the blastocyst forms, which occurs when there are 50 to 60 blastomeres present. Reference: William's Obstetrics; 24th edition; Chapter 5; Implantation and Placental Development", 'role': 'assistant'}]