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
Macula is 
Select and explain. 
A. Optic nerve, B. Optic tract, C. Periodic bluring of vision, D. Constant blinking
D: Constant blinking
Answer: D: Constant blinking 
Explanation: Ans. Constant blinking