This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Growth and development, Subject name: Pediatrics
[{'content': 'In a child, one should be worried if \nSelect and explain. \nA. Stammering occurs at 3 years, B. Lack of Toilet control at 2.5 years, C. Teeth do not erupt by 11 months, D. Social smile absent by 10 weeks', 'role': 'user'}, {'content': 'Answer: D \nExplanation: .ge 2 months 3 months 6 months 9 months 12 months 15 months 18 months 2 years 3 years 4 years 5 years Milestone . . ( mile after being talked to) social smile s ther* anticipates feeds Recognizes mo * . t angers stranger anxiety Recognizes s r \' waves "bye bye" . h Called* plays simple ball game comes w en \' Jargon . Copies parents in task (~.g. sweeping) f food drink toilet; pulls people to Asks or * \' show toys Shares toys; knows full name and gender Plays cooperatively in a group; goes to toilet alone Helps in household tasks, dresses and undress', 'role': 'assistant'}]