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
What is the angle subtended by the topmost letter in the Snellen's chart at the Nodal point of the eye when the person seeing it at 6m from the chart? 
Select and explain. 
A. 5 min, B. 10 min, C. 40 min, D. 50 min
D: 50 min
Answer: D: 50 min 
Explanation: The topmost letter subtends 5 min at Nodal point of the eye when viewed from 60 m.
So the same letter subtends 50 min at Nodal point of the eye when viewed from 6 m (By cross multiplication).