This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Ophthalmology
[{'content': "Visual acuity in infants is tested with the help of \nSelect and explain. \nA. Landolt's rings, B. '4' dot test, C. Perimeter, D. Slit lamp", 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]