This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Implantation occurs at ? 
Select and explain. 
A. 2-3 days, B. 6-7 days, C. 15-20 days, D. 20-25 days
B: 6-7 days
Answer: B: 6-7 days 
Explanation: Ans. is 'b' i.e., 6-7 days