This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Pathology
Peptic ulcer is caused by 
Select and explain. 
A. H. pylori, B. Campylobacter jejuni, C. Pneumocystis carinii, D. Crypto sporidium
A: H. pylori
Answer: A: H. pylori 
Explanation: A. i.e. (H. pylori) (594 - Basic pathology 8th)PEPTIC ULCER - two conditions are key for the development of peptic ulcers1. H. pylori infection(i) 70 - 90% persons with duodenal ulcer(ii) 70% persons with gastric ulcers2. Mucosal exposure to gastric acid and pepsin* NSAIDs are the major cause of peptic ulcer disease in persons who do not have H. pylori infection