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 is an aromatase inhibitor ? \nSelect and explain. \nA. Tamoxifen, B. Letrozole, C. Danazol, D. Taxane', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]