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 purine base contains an amino group at carbon 6? \nSelect and explain. \nA. Guanine, B. Uracil, C. Adenine, D. Cytosine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Reference: Harpers illustrated biochemistry 30th edition', 'role': 'assistant'}]