This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Nitrogen atoms of Urea contributed by: \nSelect and explain. \nA. Ammonium and aspartate, B. Ammonium and glutamate, C. Ammonium and glycine, D. Ammonium and asparagine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Ammonium and aspartateFirst nitrogen by Ammonium ion--by the reaction CPS-1Second nitrogen by Aspartate--by the reaction Argininosuccinate Synthetase', 'role': 'assistant'}]