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 10-year-old child with primary molars in various stages of exfoliation has a slight crowding in the lower anterior. The clinician should: \nSelect and explain. \nA. Observe him after 1 year, B. Obtain study casts and perform arch-length\tanalysis, C. Observe him after 6 months, D. Delay the treatment until all permanent teeth erupt', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]