This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'Which of the following is not a pyrimidine? \nSelect and explain. \nA. Ubracil, B. Thymine, C. Adenine, D. Cytosine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Adenine is a purine and not a pyrimidine Ref-Sathyanarayana 4/e', 'role': 'assistant'}]