This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Reproductive physiology and hormones in females, Subject name: Gynaecology & Obstetrics
The earliest morphological evidence of ovulation on endometrial biopsy is : 
Select and explain. 
A. Pseudostratification, B. Basal vacuolation, C. Decrease in glycogen content, D. Predecidual reaction
B: Basal vacuolation
Answer: B: Basal vacuolation 
Explanation: Endometrial biopsy Consists of curretting small pieces of endometrium from the uterus with small endometrial biopsy curette, preferably 1-2 days prior to menstruation Material removed is fixed immediately in formalin saline Secretory changes (basal vacuolation) proves that cycle has been ovulatory Ref: Shaw's Textbook of Gynaecology, 15th edition, page no: 215