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
H. pylori infection causes carcinoma by which mechanism- 
Select and explain. 
A. Production of nitrosamines, B. Gastric metaplasia, C. Increasing acid secretion, D. Causing mutation
B: Gastric metaplasia
Answer: B: Gastric metaplasia 
Explanation: None