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
Irreversible step (s) in glycolysis is/are: 
Select and explain. 
A. Hexokinase, B. Phosphofructokinase, C. Pyruvate kinase, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: All of the above