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
All of the following agents may be used for post coital contraception except: 
Select and explain. 
A. Danazol, B. CuT, C. RU - 486, D. High dose estrogen
A: Danazol
Answer: A: Danazol 
Explanation: None