This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Anatomy
After how many days of ovulation embryo implantation occurs 
Select and explain. 
A. 3-5 days, B. 7-9 days, C. 10-12 days, D. 13-15 days
B: 7-9 days
Answer: B: 7-9 days 
Explanation: Implantation is the process by which the blastocyst penetrates the uterine mucosa to get implanted in the endometrium.It stas on 6- 7 day after ovulation. Ref:JB Sharma Obs pg 20.