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
Luteal phase is best diagnosed by : 
Select and explain. 
A. Serum progesterone levels, B. Endometrial biopsy, C. Basal body temperature, D. Ultrasonography
B: Endometrial biopsy
Answer: B: Endometrial biopsy 
Explanation: Endometrial biopsy