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: Gynaecology & Obstetrics
By which day after feilization, is placental circulation established : 
Select and explain. 
A. 11th day, B. 13th day, C. 15th day, D. 17th day
D: 17th day
Answer: D: 17th day 
Explanation: 17th day