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
Distant direct ophthalmoscopy is done at a distance of: 
Select and explain. 
A. 20 cm., B. 25 cm., C. 50 cm., D. 100 cm.
B: 25 cm.
Answer: B: 25 cm. 
Explanation: B i.e. 25 cm