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: Pharmacology
[{'content': 'Alkylating drugs attach alkyl group to _________ position of guanine \nSelect and explain. \nA. N3, B. N5, C. N7, D. N9', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Alkylating drugs attach alkyl group to N7 of Guanine and results in mispairing of nitrogenous bases.', 'role': 'assistant'}]