This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
[{'content': 'A 62-year-old man presents with dark tarry stools and light-headedness. Upper endoscopy finds an ulcerating lesion in his stomach and biopsies confirm gastric cancer. Which of the following is a risk factor for carcinoma of the stomach? \nSelect and explain. \nA. Helicobacter pylori infection, B. high socioeconomic status, C. high protein diet, D. high alcohol consumption', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Low dietary vitamin C, and high salt and nitrate consumption predispose to gastric cancer, as does ingestion of smoked foods. Smoking is a risk factor, but alcohol is not. H. pylori is another important risk factor, since it causes gastritis that eventually leads to chronic atrophic gastritis, metaplasia, dysplasia, and then carcinoma.', 'role': 'assistant'}]