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
[{'content': 'Most common non protein nitrogenous fraction of\nblood: \nSelect and explain. \nA. Urea, B. Uric acid, C. Urobilinogen, D. Creatinine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]