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: Physiology
Which of the following contain C-21: 
Select and explain. 
A. Testosterone, B. Estrogen, C. Androgen, D. Progesterone
D: Progesterone
Answer: D: Progesterone 
Explanation: D i.e. Progesterone