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 patient of Acute lymphocytic leukemia with fever and neutropenia develops diarrhoea after administration of amoxicillin therapy, which of the following organism is most likely to be the causativeagent - 
Select and explain. 
A. Salmonella typhi, B. Clostridium difficile, C. Clostridium perfringens, D. Shigella flexneri
B: Clostridium difficile
Answer: B: Clostridium difficile 
Explanation: Ans. is 'b' i.e., Clostridium difficile