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: Surgery
Most common cause of anorectal abscess is - 
Select and explain. 
A. Inflammation of anal gland, B. Folliculitis, C. Inflammation of rectal mucosa, D. Rectum
A: Inflammation of anal gland
Answer: A: Inflammation of anal gland 
Explanation: None