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: Surgery
In a patient of head injury which is more important to note first: 
Select and explain. 
A. Pupillary light reflex, B. Pupillary size, C. Corneal reflex, D. Ability to open eye
D: Ability to open eye
Answer: D: Ability to open eye 
Explanation: None