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
Sources of the nitrogen in urea cycle are 
Select and explain. 
A. Aspartate and ammonia, B. Glutamate and ammonia, C. Arginine and ammonia, D. Uric acid
A: Aspartate and ammonia
Answer: A: Aspartate and ammonia 
Explanation: Sources of Nitrogen in urea are ammonia and aspartate.