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
The average distance of the fovea from the temporal margin of the optic disc is: 
Select and explain. 
A. 1 disc diameter, B. 2 disc diameter, C. 3 disc diameter, D. 4 disc diameter
B: 2 disc diameter
Answer: B: 2 disc diameter 
Explanation: 2 disc diameter