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: Microbiology
[{'content': 'All of the following are true about Helicobacter pylori except - \nSelect and explain. \nA. About 50% of world population affected, B. 85% of population is affected in some developing contries, C. All childrens in developing countries have immunity by five years of age, D. Infection is common in low socioeconomic status', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]