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: Anatomy
"Sub mucosal" glands are present in which one of the following organs? 
Select and explain. 
A. Duodenum, B. Colon, C. Anal canal, D. Stomach
A: Duodenum
Answer: A: Duodenum 
Explanation: Duodenum