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
[{'content': 'First carbon of pentose sugar of nucleic acid joins \nSelect and explain. \nA. N-9 of pyrimidine, B. N-1of pyrimidine, C. N-1 of purine, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Pentose sugar present in DNAs is deoxyribose and in RNAs it is ribose. A pentose sugar (ribose or deoxyribose) is linked to a nitrogenous base (purine or pyrimidine) covalent N-glycosidic bond to form nucleoside. This linkage joins the Carbon-I of pentose sugar with nitrogen-9 of the purine base or nitrogen-I of pyrimidine base.', 'role': 'assistant'}]