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
[{'content': 'Maximum action of corpus luteum is at ......... day: \nSelect and explain. \nA. 7, B. 9, C. 11, D. 22', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 22', 'role': 'assistant'}]