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
Which of the following drug is an antihormonal substance used to induce ovulation? 
Select and explain. 
A. Raloxifen, B. Tamoxifen, C. Mefiprestone, D. Clomiphene citrate
D: Clomiphene citrate
Answer: D: Clomiphene citrate 
Explanation: Clomiphene citrate is a nonsteroidal estrogen antagonist that increases FSH and LH levels by blocking estrogen negative feedback at the hypothalamus. Clomiphene citrate is approved by the FDA, as an ovulation-inducing drug. It is given orally in dosages of 50 to 100 mg/d for 5 days on a monthly basis to induce ovulation in infeile women. Ref: Textbook of gynecology by D C Dutta 4th Edition, Page 486-7.