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
The most frequent non-sporing anaerobic bacilli isolated from clinical specimens is 
Select and explain. 
A. Bacteroides fragilis, B. Clostridium tetani, C. Prevotella melaninogenica, D. Fusobacterium nucleatum
A: Bacteroides fragilis
Answer: A: Bacteroides fragilis 
Explanation: None