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: Dental
[{'content': 'In children below 5 years of age, most common cause of gingivitis is \nSelect and explain. \nA. local irritating factors, B. herpes, C. vitamin deficiency, D. malocclusion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]