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
Ferning of cervical mucus disappears after -day of menstrual cycle 
Select and explain. 
A. 7th, B. 15th, C. 18th, D. 21st
D: 21st
Answer: D: 21st 
Explanation: 21st