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
Implantation occurs at:- 
Select and explain. 
A. 5th day after feilization, B. 7th day after feilization, C. 8th day after feilization, D. 9th day after feilization
B: 7th day after feilization
Answer: B: 7th day after feilization 
Explanation: Implantation of blastocyst in uterine cavity occurs on 6-7th day after feilization.