This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nucleotides, Subject name: Biochemistry
[{'content': 'All of the following are true about the structure of bases found in nucleotides, EXCEPT \nSelect and explain. \nA. Purine ring is nine-membered, B. Pyrimidine ring is six-membered, C. Purine and pyrimidine rings are heterocyclic in nature, D. Imino and lactim form of purine bases are more stable', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Purine and Pyrimidine Purines and pyrimidines are nitrogen-containing heterocycles Purines and pyrimidines exhibit tautomerism. The oxo and amino groups of purines and pyrimidines exhibit keto-enol and amine-imine tautomerism. Physiologic conditions strongly our the amino and oxo forms. Purine - 9 membered ring Pyrimidine - 6 membered ring', 'role': 'assistant'}]