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: Medicine
All the following drugs are used for the induction of ovulation except -a) Clomiphene citrateb) Gonadotrophinsc) Danazold) Corticosteroids 
Select and explain. 
A. ab, B. bc, C. cd, D. ac
C: cd
Answer: C: cd 
Explanation: None