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: Pathology
Duodenal ulcer is most commonly caused by: March 2013 (c, d, e) 
Select and explain. 
A. GERD, B. NSAID therapy, C. Stress ulcer, D. H. pylori
D: H. pylori
Answer: D: H. pylori 
Explanation: Ans. D i.e. H. pylori Peptic ulcer/Peptic ulcer disease It is defined as mucosal erosions equal to or greater than 0.5 cm. As many as 70-90% of such ulcers are associated with Helicobacter pylori, a helical-shaped bacterium that lives in the acidic environment of the stomach. Four times as many peptic ulcers arise in the duodenum--the first pa of the small intestine, just after the stomach--as in the stomach itself. About 4% of gastric ulcers are caused by a malignant tumor, so multiple biopsies are needed to exclude cancer. Duodenal ulcers are generally benign.