This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa 1 (History, Microscopy, Stains and Structure and Physiology of Bacteria), Subject name: Microbiology
Longest pathogenic Bacillus species is 
Select and explain. 
A. Bacillus subtilis, B. Bacillus cereus, C. Bacillus anthracis, D. Bacillus megaterium
C: Bacillus anthracis
Answer: C: Bacillus anthracis 
Explanation: Longest pathogenic Bacillus species is Bacillus anthracis (1.2 mm width and 3-5mm long). B. anthracis causes anthrax Largest known Bacillus species is B. megaterium, (1.5 mm width and 4 mm long).