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': 'Spacing in anterior teeth in deciduous dentition \nSelect and explain. \nA. Common and desirable, B. Uncommon and undesirable, C. Common and undesirable, D. Uncommon', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]