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': 'Sources of the nitrogen in urea cycle are the following: \nSelect and explain. \nA. Aspaate and ammonia, B. Glutamate and ammonia, C. Arginine and ammonia, D. Uric acid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The 2 nitrogen atoms of urea are derived from two sources, one from ammonia and other from alpha amino group of aspaic acid. Ref: Textbook of Biochemistry By DM Vasudevan, 3rd Edition, Pages 163-5', 'role': 'assistant'}]