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': 'Which of the following drugs is topoisomerase I inhibitor? \nSelect and explain. \nA. Doxorubicin, B. Irinotecan, C. Etoposide, D. Vincristine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Camptothecin derivatives like topotecan and irinotecan act by inhibiting topoisomerase-I whereas Epipodophyllotoxins (etoposide and teniposide) and anthracyclines (doxorubicin, daunorubicin etc.) act by inhibiting topoisomerase-II.', 'role': 'assistant'}]