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
Maximum action of corpus luteum is at ......... day: 
Select and explain. 
A. 7, B. 9, C. 11, D. 22
D: 22
Answer: D: 22 
Explanation: 22