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
C peptide is pa of: 
Select and explain. 
A. Pro-insulin, B. Insulin, C. ACTH, D. Growth hormone
A: Pro-insulin
Answer: A: Pro-insulin 
Explanation: C-peptide is a peptide that is made when proinsulin is split into insulin and C-peptide.