This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'McFadyean reaction is seen in: \nSelect and explain. \nA. Yersinia pestis, B. Clostridium perfringens, C. Bacillus anthrax, D. Staphylococcus aureus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ref: Harrisons 19th ed. pg. 261e2 \\* McFadyean reaction is a special staining reaction, demonstrating a pink capsule around a blue cell, after staining with methylene blue, which is used as a presumptive diagnosis for anthrax in a blood smear.* Anthrax is caused by B. anthracis a Gram-positive, nonmotile, spore-forming rod that is found in soil and predominantly causes disease in herbivores such as cattle, goats, and sheep.', 'role': 'assistant'}]