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
Snellen's test types are based on the fact that two distant points can be visible as separate only when they subtend at the nodal point of the eye an angle of: 
Select and explain. 
A. 1 minute, B. 3 minute, C. 5 minute, D. 2 minute
A: 1 minute
Answer: A: 1 minute 
Explanation: Ans. 1 minute