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': "According to Mahler's theory, the period of childhood is divided into: \nSelect and explain. \nA. Normal autistic phase, B. Normal symbiotic phase, C. Separation industrialisation phase, D. All of the above", 'role': 'user'}, {'content': "Answer: D \nExplanation: According to Mahler's theory, the period of childhood is divided into three stages.\n\nNormal autistic phase (0 - 1 year)\nNormal symbiotic phase (4 wks to 4 yrs)\nSeparation individualization phase (5 to 36 months)", 'role': 'assistant'}]