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
A man, after skinning a dead animal, developed a pustule on his hand. A smear prepared from the lesion showed the presence of Gram positive bacilli in long chains which were positive for McFadyean's reaction. The most likely aetiological agent is-( 
Select and explain. 
A. Clostridium tetani, B. Li steria monocytogenes, C. Bacillus anthracis, D. Actinomyces sp
C: Bacillus anthracis
Answer: C: Bacillus anthracis 
Explanation: Ans. is 'c' i.e., Bacillus anthracis . Mc Fadyean's reaction is used for the presumptive diagnosis of anthrax. . History of skinning a dead animal, development of pustule, the presence of gram (+)ve bacilli in long chains with positive Mc Fadyean's reaction are suggestive of "anthrax" caused by Bacillus anthracis.