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
Embryo implanted in uterus by ? 
Select and explain. 
A. 14 days, B. 28 days, C. 8 weeks, D. 24 weeks
A: 14 days
Answer: A: 14 days 
Explanation: None