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
Which of the following organs is the most common site of origin of the tumour associated with the Zollinger-Ellison syndrome - 
Select and explain. 
A. Duodenum, B. Lymph nodes, C. Spleen, D. Pancreas
A: Duodenum
Answer: A: Duodenum 
Explanation: Ans. is 'a' i.e., Duodenum