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': 'A 7-year-old has a 4-mm maxillary midline diastema. Which of the following should be done? \nSelect and explain. \nA. Brackets should be placed to close it., B. A radiograph should be taken to rule out the presence of a supernumerary tooth., C. Nothing should be done. It will close on its own., D. Nothing should be done. Treatment should be deferred until the rest of the permanent dentition erupts.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: When a large diastema greater than 2 mm is present, it will probably not close on its own. Diagnostic tests, such as a radiograph, should be accomplished to rule out the presence of a supernumerary tooth, usually a mesiodens.', 'role': 'assistant'}]