This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
Non-protein nitrogen product in food 
Select and explain. 
A. Sucrose, B. Triglyceride, C. Urea, D. Cholesterol
C: Urea
Answer: C: Urea 
Explanation: NPN refers to all N2containing substances other than proteins. include urea, uric acid, creatinine.