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: Ophthalmology
[{'content': 'Which of the following is the drug used for testing errors of refraction in a 7-year-old girl? \nSelect and explain. \nA. Atropine ointment, B. Tropicamide, C. Phenylephrine, D. Homatropine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Atropine is a powerful cycloplegic. It is needed to overcome the muscle tone.', 'role': 'assistant'}]