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: Biochemistry
X can be denoted by which of the following proteins involved in the iron metabolism? 
Select and explain. 
A. Hepcidin, B. Albumin, C. Transferrin, D. Ferroportin
A: Hepcidin
Answer: A: Hepcidin 
Explanation: None