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: Microbiology
[{'content': 'Inveed fir tree appearance is characteristic ? \nSelect and explain. \nA. Bacillus anthrax, B. Hemophilus influenzae, C. Yersinia pestis, D. Brucella', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Bacillus anthrax", 'role': 'assistant'}]