This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Total number of molecules of ATP required for denovo purine synthesis? 
Select and explain. 
A. 2, B. 5, C. 6, D. 4
B: 5
Answer: B: 5 
Explanation: Reference: Harpers illustrated biochemistry 30th edition