This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Growth, Development, and Behavior, Subject name: Pediatrics
[{'content': "An infant can regard his parent's face, follow to midline, lift his head from the examining table, smile spontaneously, and respond to a bell. He does not yet regard his own hand, follow past midline, nor lift his head to a 45deg angle off the examining table. Which of the following is the most likely age of the infant? \nSelect and explain. \nA. 1 month, B. 3 months, C. 6 months, D. 9 months", 'role': 'user'}, {'content': 'Answer: A \nExplanation: At one month, infants typically regard face, follow items to the midline, begin to vocalize, respond to a bell, and lift their head from the examining table. An 8-week-old child normally should be able to smile and coo when smiled at or talked to. Not until about 3 months of age would an infant be expected to follow a moving toy from side to side and also in the vertical plane.', 'role': 'assistant'}]