This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Internal Generative Organs, Subject name: Gynaecology & Obstetrics
[{'content': 'Zygote with zona pellucida reaches uterine cavity by- \nSelect and explain. \nA. 2 days, B. 4 days, C. 5 days, D. 6 days', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans-B lets revise some imp points:- 1-morula=16 cell stage 2-blastocyst hatching/ZP removal/implantation=5-12 days after fertiization(5-7 days) 3-sequence of reactions is alphabetical=acrosome rxn f/b cortical rxn f/b zona reaction. 4-conceptus reaches uterine cavity in 32cell stage. 5-transvaginal insertion of coceptus 8 cell stage. 6- spermatogenesis is completed in 74 days 7-trophoblast differentiates into cyto and syncytio day 6. 8- ovulation occurs 10-12 hrs before LH PEAK. 9-LH SURRGE occurs 34-36 hrs before ovulation.', 'role': 'assistant'}]