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: Medicine
[{'content': 'All are true regarding Helicobacter pylori except - \nSelect and explain. \nA. Less prevalent in developing countries, B. Toxigenic strains usually causes ulcers, C. Urea breath is positive, D. Gram negative organism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]