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
Ampicillin prophylaxis is given in ? 
Select and explain. 
A. Rectal surgery, B. Splenectomy, C. Head and neck surgery, D. Biliary surgery
A: Rectal surgery
Answer: A: Rectal surgery 
Explanation: Ans. is 'a' i.e., Rectal