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 earliest symptom to occur in corneal ulcer is 
Select and explain. 
A. Pain, B. Photophobia, C. Loss of sensation, D. Diminished vision
A: Pain
Answer: A: Pain 
Explanation: Ans. Pain