This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pathology of Conception, Subject name: Gynaecology & Obstetrics
Patient is being treated with clomiphene for infertility, method of choice to look for ovulation is - 
Select and explain. 
A. Serial ultrasound, B. Chest X-ray, C. Serial HCG, D. None
A: Serial ultrasound
Answer: A: Serial ultrasound 
Explanation: Ans. is 'a' Serial ultrasound (Ref. Shaws, 13/e, p 305 (12/e, p. 242)).In patients with infertility and being treated with clomiphene monitoring of Graafian follicle is required to check its maturity and to detect imminent ovulation.This monitoring is done with serial ultrasound starting from day 10th to day 16th.It is non-invasive, safe and accurate method and is the standard investigation to detect ovulation.