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': 'Distant direct ophthalmoscopy is done at a distance of: \nSelect and explain. \nA. 20 cm., B. 25 cm., C. 50 cm., D. 100 cm.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. 25 cm', 'role': 'assistant'}]