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
Syncytiotrophoblasts and cytotrophoblasts differentiate on what day after the feilization? 
Select and explain. 
A. 6 days, B. 8 days, C. 10 days, D. 12 days
B: 8 days
Answer: B: 8 days 
Explanation: 8 days