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': 'Not present in DNA \nSelect and explain. \nA. Uracil, B. Thymine, C. Cystosine, D. Adenine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Repeated question', 'role': 'assistant'}]