This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Social and Language Milestones, Subject name: Pediatrics
[{'content': 'A child has staed mouthing objects, shows likes and dislikes, but has not yet developed stranger anxiety. The age of child is: \nSelect and explain. \nA. 3 months, B. 5 months, C. 7 months, D. 9 months', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Stranger anxiety, that develops at around 7 months has not yet appeared. So, the age of the child is 5 months. Child stas mouthing object: 5-6 months.', 'role': 'assistant'}]