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: Physiology
Tumor of which of the following type of cells result in Zollinger Ellison syndrome? 
Select and explain. 
A. ECL cells, B. Chief cells, C. G cells, D. S cells
C: G cells
Answer: C: G cells 
Explanation: Zollinger Ellison syndrome is a malignancy of the gastrin secreting G cells present in the antral mucosa of the stomach. Parietal cells secrete acid and intrinsic factor, chief cells secretes pepsinogen, ECL cells synthesize histamine, and secretin is synthesized by the S cells of the duodenum. Ref: LANGE'S Gastrointestinal Physiology By Kim E Barrett chapter 3.