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': 'Most common cause of chronic inflammation of the gingiva in a preschool child \nSelect and explain. \nA. Acute herpetic gingivostomatitis, B. Acute necrotising gingivitis, C. Apthous stomatitis, D. Vitamin B deficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]